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Hello Group
Having just refined and improved my Polar Alignment, of my permanent pier mount G11 using Sharp Cap, I am now keen to get into guided imaging.
I did the PA adjustment using my DSLR camera connected to one of my side-by-side main scopes, a Sky 90. The other scope on the mount saddle is a C 9.25.
My thinking is to remove the C9.25 from the saddle then add a new guide scope [make/size/FL yet to be selected] to replace the C9.25 and then reposition and rebalance this new Sky90/Guide Scope combo.
My question concerns the Guide Scope - is mounting the GS onto the side by side saddle, rather than on top of the Sky90, an acceptable arrangement?
I anticipate the distance between the centre axis of the imaging and guiding scopes to be around 7". I presume I would need to aim the Guide Camera to match the Sky90's target/FOV.
If anyone would like to also recommend a Guide Scope for use with a ZWO ASI120MM MINI Guide Camera then I shall be very pleased to see these. ??
Many Thanks
Terry [uk] ????
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I like my Orion 9X60 guide scope with its focus control. Pairs with my ASI290mm well.
Mearl
On Mon, Dec 14, 2020, 12:56 PM Terry Pullen via <tpullen152= [email protected]> wrote: Hello Group
Having just refined and improved my Polar Alignment, of my permanent pier mount G11 using Sharp Cap, I am now keen to get into guided imaging.
I did the PA adjustment using my DSLR camera connected to one of my side-by-side main scopes, a Sky 90. The other scope on the mount saddle is a C 9.25.
My thinking is to remove the C9.25 from the saddle then add a new guide scope [make/size/FL yet to be selected] to replace the C9.25 and then reposition and rebalance this new Sky90/Guide Scope combo.
My question concerns the Guide Scope - is mounting the GS onto the side by side saddle, rather than on top of the Sky90, an acceptable arrangement?
I anticipate the distance between the centre axis of the imaging and guiding scopes to be around 7". I presume I would need to aim the Guide Camera to match the Sky90's target/FOV.
If anyone would like to also recommend a Guide Scope for use with a ZWO ASI120MM MINI Guide Camera then I shall be very pleased to see these. ??
Many Thanks
Terry [uk] ????
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On 12/14/2020 1:26 PM, Mearl Balmer wrote: I like my Orion 9X60 guide scope with its focus control. Pairs with my ASI290mm well.
Mearl Mearl, I have the Agena version of that same scope and also the ASI290. I have never been happy with the size of the stars. Initially they looked awful. Adding a UV/IR filter helped some and adding a minus-violet filter helped more. But the HFD never is less than maybe 4+ no matter how carefully I focus. In places they show very noticeable coma. Agena thinks the issue might be the objective and they are kindly sending a replacement scope which I have not received yet. But since you have the same setup.....how do your stars look? What is a typical HFD? I have always wondered what to expect on an inexpensive scope but Agena could not tell me what a reasonable HFD would be even though this is a pretty common setup and the scope is supposed to be a guide scope. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Paul, With good sky, and good focus, I get stars hfd bouncing around from high 2 to 5.?? Guiding is still good with 3? - 4. Mearl
On Mon, Dec 14, 2020, 1:42 PM Paul Goelz < pgoelz@...> wrote: On 12/14/2020 1:26 PM, Mearl Balmer wrote:
> I like my Orion 9X60 guide scope with its focus control. Pairs with my
> ASI290mm well.
>
> Mearl
Mearl,
I have the Agena version of that same scope and also the ASI290.? I have
never been happy with the size of the stars.? Initially they looked
awful.? Adding a UV/IR filter helped some and adding a minus-violet
filter helped more.? But the HFD never is less than maybe 4+ no matter
how carefully I focus.? In places they show very noticeable coma.
Agena thinks the issue might be the objective and they are kindly
sending a replacement scope which I have not received yet.? But since
you have the same setup.....how do your stars look?? What is a typical
HFD?
I have always wondered what to expect on an inexpensive scope but Agena
could not tell me what a reasonable HFD would be even though this is a
pretty common setup and the scope is supposed to be a guide scope.
Paul
--
Paul Goelz
Rochester Hills, MI? USA
pgoelz@...
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Putting the guide scope side-by-side with a fairly short focal length imaging scope is fine, but if you¡¯re going to use the C9.25 for imaging it¡¯s best to piggyback the guide scope. ?Guide scopes can be surprisingly small, so a good solution would be to piggyback the guider on the C9.25. ?Unless you¡¯re pushing to the total weight limit, that should work pretty well.
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On Dec 14, 2020, at 9:56 AM, Terry Pullen via <tpullen152@...> wrote:
?Hello Group
Having just refined and improved my Polar Alignment, of my permanent pier mount G11 using Sharp Cap, I am now keen to get into guided imaging.
I did the PA adjustment using my DSLR camera connected to one of my side-by-side main scopes, a Sky 90. The other scope on the mount saddle is a C 9.25.
My thinking is to remove the C9.25 from the saddle then add a new guide scope [make/size/FL yet to be selected] to replace the C9.25 and then reposition and rebalance this new Sky90/Guide Scope combo.
My question concerns the Guide Scope - is mounting the GS onto the side by side saddle, rather than on top of the Sky90, an acceptable arrangement?
I anticipate the distance between the centre axis of the imaging and guiding scopes to be around 7". I presume I would need to aim the Guide Camera to match the Sky90's target/FOV.
If anyone would like to also recommend a Guide Scope for use with a ZWO ASI120MM MINI Guide Camera then I shall be very pleased to see these. ??
Many Thanks
Terry [uk] ????
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On 12/14/2020 2:23 PM, Mearl Balmer wrote: Paul,
With good sky, and good focus, I get stars hfd bouncing around from high 2 to 5.
Guiding is still good with 3? - 4.
Mearl Thanks Mearl, that gives me hope that the replacement scope will be an improvement. I have always assumed my guiding is OK but since this is my first attempt at guiding I have nothing to compare it to. Brian suggested my guide logs looked noisy and I was wondering if that could be because my stars were too soft, making the centroid measurement less precise. Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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Hi Terry, Welcome to the group!
I'm an owner of a young GM811GHD, about 10 months old now. Gemini II
Guiding scopes are comparatively smaller than your Main telescopes. If your Sky90 has a guider shoe on it, that would be a good starting place for a Guide Scope and Camera.
I tried real hard to use an Off-Axis Guider (OAG) for a month. When I got a Guide Scope, and abandoned my attempt at an OAG, I found instant success.
I still stumbled around with PHD 1 but eventually got it working. And jumped in when PHD2 was released.
Most recently I I've got on the PHD2 multi star release. And just a short while back I upgraded my guiding camera to a ZWO ASI290MM Mini.
But a 50-60 mm guide scope will work fine with your ASI120. And you could probably just leave the C9.25 in place.
Guiding is just another step to nirvanas.
--
SonnyE
(I suggest viewed in full screen)
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Hi Terry,
A C925 Edge HD is what I have and usually I mount an Orion CT-80 on top as the guide scope. Please see pics. The CT-80 (FL-400mm) is not great for photography but is more than adequate for guiding. With a 0.7X FR, the C925 goes from 2350 to 1645 mm FL, so a 400mm guide scope fits into that thumb rule of guide to main scope FL ratio of 20-25%. It would probably be OK without the focal reducer too.
But on top of the C925 I have a Losmandy DC 9.25 dovetail made specifically for that scope. And I also use the DVR 108/66 scope rings. This ring set has two to hold the guide scope, and another smaller one to hold onto the extensions for the guide camera, so you don't have to worry about flexure of the focuser rack?causing guiding error when the mount changes position over the course of an evening. This was a nice idea the Losmandy came up with.
Hope this info gives you some ideas.
Regards,
John
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Regarding your experience, Paul of Rochester Hills (Livonia was my old stomping grounds) , I received one of these 60mm guiders (direct from China on Ebay) when they first came out a few years ago.
When looking thru it with an eyepiece I noticed similar problems.
I suspected that the objective had been installed backwards. So all I had to do was unscrew the front and flip the (cemented) lens. Problem solved.
I notified the factory in case they had an assembler/fitter who needed a bit of training.
The images are generally fine now. Never worried about HFD, FWHM or any other parameter. But having to had a filter (beyond the cut filter in the camera) should not be necessary.
By the way, you don't want absolutely perfect focus on a guider - if the centroid algorithms are anything like the norm, the more pixels the better, assuming the image doesn't become too dim.
But you don't want coma.
Cheers,
Mark Christensen
St. Charles, IL
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On 12/15/2020 11:38 AM, Mark Christensen wrote: Regarding your experience, Paul of Rochester Hills (Livonia was my old stomping grounds) , I received one of these 60mm guiders (direct from China on Ebay) when they first came out a few years ago.
When looking thru it with an eyepiece I noticed similar problems.
I suspected that the objective had been installed backwards. So all I had to do was unscrew the front and flip the (cemented) lens. Problem solved.
I notified the factory in case they had an assembler/fitter who needed a bit of training.
The images are generally fine now. Never worried about HFD, FWHM or any other parameter. But having to had a filter (beyond the cut filter in the camera) should not be necessary.
By the way, you don't want absolutely perfect focus on a guider - if the centroid algorithms are anything like the norm, the more pixels the better, assuming the image doesn't become too dim.
But you don't want coma.
Cheers,
Mark Christensen
St. Charles, IL Thanks for that! When I first got the scope I wanted to remove the dew shield to make the overall length shorter. That is when I discovered that the dew shield also holds the objective in place. when the objective fell out, I lost track of which was was front so I tried it both ways and backwards from what it currently is... is much worse. I am aware that single pixel stars are not good but without the minus violet filter they are VERY blobby. With the minus violet they are quite a bit better which says to me there is purple fringing sufficient to degrade a monochrome image. There is also coma in a good part of the FOV. All of which I have to assume will degrade the accurate determination of a stable centroid in anything less than perfect seeing? FWIW, with a 30mm eyepiece it looks great. But put in a 4.5mm Lanthanum eyepiece for a view similar to the FOV with the guide camera and the image is not at all sharp and very low contrast. Funny.... I grew up in Glenview (NW of Chicago) and lived many years in Evanston before I moved to SE Michigan ;) Paul -- Paul Goelz Rochester Hills, MI USA pgoelz@... www.pgoelz.com
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I have a GM811G along with an EdgeHD8 which is smaller, but similar to your setup. I always prefer an OAG as it performs much better, but I sometimes have to use a guide scope. I have a Hyperstar which puts the camera on the front of the scope and I don't want an OAG obscuring the view even more. So for this case I use the guide scope. I also use the guide scope when I simply can't find any guide stars with the OAG. I also chose the ZWO 178 camera since it has a fairly large chip which gives me a better chance of finding a guide star when using the OAG.? I found this pretty cheap OAG is actually better than the Orion one I used before:?
It's got a pretty big pickoff mirror which helps with the quality of the image, and the FOV to be able to find stars.?
I also use the guide scope when I simply can't find any stars to guide using the OAG. In this case I picked up this scope, again pretty cheap, but seems to be good quality and have the features I need for attaching a guide camera solidly:?
I attach the guide scope to the top of the main scope. I didn't find a good spot to add a vixen mount on the EdgeHD, so I 3D printed an adapter so I could attach it perfectly centered, and avoid weight hanging off the side. The 3D print is fairly hefty, and my results are good, so hopefully there is little to no movement between the guide and main scopes. -- This is probably the weakest link in my setup, but seems to be working fine.?
I also 3d printed a?bahtinov mask for the guide scope so I'm able to get very good focus. Here's? links to the 3D models I made. They're freely available if you've got a 3D printer -- which I highly recommend for this hobby!
Vixen mount: I don't think that this will work for your 9.25 since it will have a different diameter.?
Mask and cap for the guide scope:
My setup is working well for me, so that's what I recommend to you. Everyone takes their own path through this hobby though -- clear skys!!
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Hi John, I had been using a SV50mm guidescope with QHY5L-II mono autoguider very rigidity mounted using the Stellarvue non-adjustable clamshell fasted to the top dovetail of the imaging optic.? I recently switched to all ZWO to use the ASIAIR-PRO so I have no data from this equipment yet. But a few years ago I was out in the eastern Sierra testing a classic Losmandy straight drivetrain 2-piece worm block G11 with a Gemini 1 I ran a couple of quick guided PE tests with my usual 50mm guidescope piggybacked and at prime focus of a M10" f/6.3 SCT OTA. The guiding results were a surprise to me because they were virtually inidentical. Both runs were well under <0.5" PE RMS, more typically centered on 0.4" RMS. Based on these results I see no reason use a large scope for guiding and the only reason to use an OAG as far as I can see is mirror shift.? When I later returned for similar testing with the same mount now fully updated by Losmandy with tucked motors and spring loaded worms etc. the results were not surprising and again virtually identical. This tells me there is something else in the system that is limiting improvement of guided PE of this system. But with this level of autoguided PE I'm not going to lose any sleep over it.? I did buy a newer smaller pixel ASI290MM-mini to see if the claims from ZWO about the smaller pixels producing improved autoguiding have any basis in fact. And to double check the math I also bought an ASI120MM-mini to use as a baseline because the QHY5L-II mono used a similar spec chip. I think the old guidelines for guided scope to imaging scope have become obsolete due to the huge improvements in sensor QE and the jumps that PHD2 have made. This is evident even from my several years old data.?
John KmetzDec 14? ?
Hi Terry,
?
A C925 Edge HD is what I have and usually I mount an Orion CT-80 on top as the guide scope. Please see pics. The CT-80 (FL-400mm) is not great for photography but is more than adequate for guiding. With a 0.7X FR, the C925 goes from 2350 to 1645 mm FL, so a 400mm guide scope fits into that thumb rule of guide to main scope FL ratio of 20-25%. It would probably be OK without the focal reducer too.
?
But on top of the C925 I have a Losmandy DC 9.25 dovetail made specifically for that scope. And I also use the DVR 108/66 scope rings. This ring set has two to hold the guide scope, and another smaller one to hold onto the extensions for the guide camera, so you don't have to worry about flexure of the focuser rack causing guiding error when the mount changes position over the course of an evening. This was a nice idea the Losmandy came up with.
?
Hope this info gives you some ideas.
?
Regards,
?
John
-- Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Hey Chip,?
From my own experience for the OAG results vs Guide scope. I have found that I may get great guiding in PHD using a guide scope, but something may shift between the guide scope and the main scope and this results in bad images but great guiding. I've also found that the OAG get's better PHD guiding results as well -- but my system does have that week link of the plastic between the guide scope and main scope.? -- Also these results were from maybe about a year ago, and PHD is a different beast now. As it stands I'm getting the best results that I've ever had, and I'm using a guide scope. When I do imaging without the Hyperstar I'll switch back to the OAG and compare.?
Jamie
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Jamie,
I am imaging with the bespoke Parallax/AT130mm f/6 apo primarily but also have a Stellarvue SV80ST25-SV I use for the wide stuff. For these scopes the piggybacked 50mm guidescope setup works great and I see no reason to use anything else. But I am curious to see if the OAG changes anything.?
?
For the last several years I have been working towards imaging with a scope I pulled out of the dumpster after I resurrected and slightly modified it - a deforked LX200 M10" f/6.3 SCT OTA. I hope to use it at three different focal lengths, 1,600mm @ f/6.3, 1,008mm @ f/4 and 640mm @ f/2.5 using Starizona reducer/flatteners. I have an ASI183MM-Pro and think it might make a really good system, it is a big enough light bucket and it can be made to work very fast. It is limited to small cameras but is a lot more flexible, a lot cheaper than a RASA and visual capable. The next step is to test the SCT II/III .63x reducer coma corrector and see if I need to make one last modification and lock the mirror down on the baffle tube and realign the optics. I have a 2.5" Moonlite focuser I think will work but it may put the reducer too far out of the baffle to work well, have to test it and see. I think the saving grace is that the small 1" format chip will avoid vignetting and any optical weirdness of having the SCT II/III reducer further back than usual. So much to do!?
--
Chip Louie Chief Daydreamer Imagination Hardware?
? ?Astropheric Weather Forecast - South Pasadena, CA?
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Lots of things to play with for sure Chip!
Other than the sct, I have a williams optics gt81 that is awesome. I've used both a guide scope and an OAG and at that focal length either works great.?
The hyperstar is similar, and some don't even guide them their so fast. I think that getting the best RMS is a hobby on its own Indipendant of imaging!
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Hi Chip,
My experiences appear to be quite different from my highly light polluted suburban backyard. I have the 80x400mm CT-80 and also a William Optics 50x200mm guidescope. Also I have the ASI290MINI (2.9 micron) and a older Lodestar X2 (8.3 micron) guide cams. With either guidescope I see virtually no change in guiding when switching back and forth between cams. I thought the more modern ASI290 with a big change in arcsec/pixel would do something great but it did not.
However, when using either guide cam, there is an improvement in guiding when going from 50mm to 80mm aperture. I see about 0.2 to 0.3" improvement in guiding error. When cutting through local light pollution, the larger aperture lets me see smaller and crisper stars I can lock onto more easily. And my local seeing is not too great either, perhaps playing a factor.
I have not tested the above combinations in dark skies for comparison. So I can only say what has worked for me locally.
Regards,
John
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Hi
Thanks to everyone for your recommendations and advice on selecting and mounting a Guidescope on my G11.
Regards
Terry
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Mearl Balmer
Jamie Amendolagine
Chip Louie