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Re: Used GM-8 Guiding Help
Thanks again Derek! I'm looking forward to testing!
Michael, Here is the link to my guide scope I was using during the first night of testing along with the ASI120mm:? The second night, however, I was using my 430mm refractor with a 0.8x focal reducer (I was sort of in a rush and didn't remove it from previous imaging sessions) for a new focal length of 344mm. Both of these were put into PECPrep with their respective graphs, I think the data is correct (unfortunately). I was able to get drift align working well for both nights which I used for analyzing, the first night I came to 0.2' polar error and the second night was at 0.8' polar error according to guiding assistant. I noticed for my mount to get a good drift align I have to let it run for a full period on the first adjustment and at least half a period for subsequent adjustments. Overall drift align takes me close to 30min, otherwise all the noise you see in these graphs start telling me the wrong stories and corrections to make :-) (this took me a while to figure out). Everything you listed is on my to-do list, and I will definitely keep this post updated! Thanks everyone for the input, I know my posts are long but I'm hoping keeping this well documented will help someone in the future as well! |
Re: Used GM-8 Guiding Help
¿ªÔÆÌåÓýThe Stellarvue 50mm finder / guider is f4 and says 210mm.. ? Similar models are ubiquitous.. ? Derek ? From: [email protected] [mailto:[email protected]] On Behalf Of Michael Herman
Sent: Thursday, January 28, 2021 4:52 PM To: [email protected] Subject: Re: [Losmandy_users_io] Used GM-8 Guiding Help ? Nick, ? One other thing puzzles me. ? You said your guide scope is 50mm f/4. I looked but could not find one. ? I have several 50mm 8X magnification guide scopes.? I'm not sure what their FL is. I did find a 50mm f3.8 from unknown brand shown online.? ?? ? But could you please double check and get the FL of that guide scope?? It's important because the PE Y axis scale depends on that FL factor.? ? ? I always recommend when testing the mount to eliminate any other variables, put a long FL refractor (no mirror flop) in the dovetail and put the autoguider camera at prime focus (or use a diagonal if necessary) to get the camera focussed.? Don't use a piggyback guide scope.? If that flops it will wipe out your data and question the analysis.?? ? You discovered that the PECprep type FFT program will try and subtract a linear error in polar drift due to unfavorable polar alignment.? It won't subtract a curvy drift error.? The solution is to eliminate excessive drift.? Best to do a drift alignment and correct as necessary before tracking the unguided star.? It only takes a few minutes to check by drift (PHD2 has a good Drift Alignment tool ...try it!) ? The bearings you ordered must be the R4ZZ ABEC-7 with kyodo grease shown here...or maybe the McMaster-Carr equivalent.? ?
? Anyway, if you do these: ?Change RA to the precision brass worm. ?Put in the better bearings. ?Replace your poor performing RA gearbox with a new one ( or the DEC gear box if it is better). ?Add the Belleville spring behind the far bearing (on both RA and DEC) (that far bearing OD must be polished down to allow the bearing to slide in the block). ?Carefully line up that key Oldham coupler ends by shifting the gearbox location, so the Oldham ends do not shift during rotation.? ? Seems like a lot but it isn't really.? You will get to the low PE that this mount is capable of delivering.?? ? After that, autoguiding will take care of any residual movement.? ?You probably won't need PEC if the natural PE gets low enough.?? ? ? Good luck!!! ? On Thu, Jan 28, 2021, 4:15 PM Nick <nicklopez1991@...> wrote:
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Re: Used GM-8 Guiding Help
Quick update:
Decided to dive into researching the bearings I purchased from McMaster Carr compared to the Boca Bearings. I was able to download each one's CAD files and open them up and get a section view, and was surprised to find a major difference not listed in the descriptions. It appears the McMaster Carr bearings are "full complement" bearings which do not include a retainer and also include 12 bearings instead of 8. Researching the differences of "full complement" bearings, it seems they are able to handle heavier loads at the expense of lower RPMs due to additional friction (more balls, and ball-ball friction). They have lighter axial loads due to risk of balls being forced out of the filling slot. In terms of loading, I'm not sure for this hobby it will make a huge difference, but I have to imagine with there being no retainer, the bearing locations during rotation is also a bit less periodic, not sure on anyone's thoughts? Honestly, if I were buying bearings again I would stick with Boca Bearings, however, I will say I still stand by the significant difference of bearing feel these had compared to my existing bearings and will continue with testing. Not sure if anyone with Boca Bearings can attest to also being buttery smooth? I would assume they are and my existing bearings are just old. Pictures below of CAD sections, pic 005 is McMaster Carr, pic 006 is Boca Bearings |
Re: Used GM-8 Guiding Help
¿ªÔÆÌåÓýThe worm will be mailed tomorrow.. ? Derek ? From: [email protected] [mailto:[email protected]] On Behalf Of Nick
Sent: Thursday, January 28, 2021 4:16 PM To: [email protected] Subject: Re: [Losmandy_users_io] Used GM-8 Guiding Help ? Wow, I am blown away by all the good info everyone has been helping out
with, thanks so much!? |
Re: 365 covers, condensation, and Wavy Washer standing water..
Sonny Edmonds
No problem here.
My CFO insists I bring my toys in at night. So mine is configured to break down for portability by mule train. And I'm the jackass carrying the parts. LOL! So when the Doctor asks if I'm getting excersize, I explain my routine to him. I doubt he could carry the mount back and forth. But my stuff stays high and dry inside the house. Glad you love your G11G. I'm lovin my G811GHD in between the Spring storms. Looks like it's going to be a really cloudy one here. -- SonnyE (I suggest viewed in full screen) |
Re: Used GM-8 Guiding Help
Nick, One other thing puzzles me. You said your guide scope is 50mm f/4. I looked but could not find one. I have several 50mm 8X magnification guide scopes.? I'm not sure what their FL is. I did find a 50mm f3.8 from unknown brand shown online.? ?? But could you please double check and get the FL of that guide scope?? It's important because the PE Y axis scale depends on that FL factor.? ? I always recommend when testing the mount to eliminate any other variables, put a long FL refractor (no mirror flop) in the dovetail and put the autoguider camera at prime focus (or use a diagonal if necessary) to get the camera focussed.? Don't use a piggyback guide scope.? If that flops it will wipe out your data and question the analysis.?? You discovered that the PECprep type FFT program will try and subtract a linear error in polar drift due to unfavorable polar alignment.? It won't subtract a curvy drift error.? The solution is to eliminate excessive drift.? Best to do a drift alignment and correct as necessary before tracking the unguided star.? It only takes a few minutes to check by drift (PHD2 has a good Drift Alignment tool ...try it!) The bearings you ordered must be the R4ZZ ABEC-7 with kyodo grease shown here...or maybe the McMaster-Carr equivalent.? Anyway, if you do these: ?Change RA to the precision brass worm. ?Put in the better bearings. ?Replace your poor performing RA gearbox with a new one ( or the DEC gear box if it is better). ?Add the Belleville spring behind the far bearing (on both RA and DEC) (that far bearing OD must be polished down to allow the bearing to slide in the block). ?Carefully line up that key Oldham coupler ends by shifting the gearbox location, so the Oldham ends do not shift during rotation.? Seems like a lot but it isn't really.? You will get to the low PE that this mount is capable of delivering.?? After that, autoguiding will take care of any residual movement.? ?You probably won't need PEC if the natural PE gets low enough.?? Good luck!!! On Thu, Jan 28, 2021, 4:15 PM Nick <nicklopez1991@...> wrote: Wow, I am blown away by all the good info everyone has been helping out with, thanks so much!? |
Re: Used GM-8 Guiding Help
¿ªÔÆÌåÓýWe are here to help like everyone helped me.. ? Thanks for the log viewer link.. I was *just* going to look for it, but decided to check email first.. ? I also found the one for diagnosing PE.. Seems mine is ¡°good enough¡± and I should stop trying to make it better or else I might make it worse, not knowing anything and all.. ? :-)) ? Derek ? From: [email protected] [mailto:[email protected]] On Behalf Of Brian Valente
Sent: Thursday, January 28, 2021 2:19 PM To: [email protected] Subject: Re: [Losmandy_users_io] Used GM-8 Guiding Help ? Derek that's very kind of you :) ? On Thu, Jan 28, 2021 at 12:07 PM Derek C Breit <breit_ideas@...> wrote:
? -- Brian? ? ? ? Brian Valente portfolio |
Re: Used GM-8 Guiding Help
Wow, I am blown away by all the good info everyone has been helping out with, thanks so much!?
Michael, I will definitely get the serial number and reach out to Losmandy just out of pure curiosity. I agree the plastic gearbox is likely a contributor to the fast oscillations. I have high hopes for the new bearings as well, they arrived today and it is night and day difference to the existing bearings. The existing ones have a very obvious jitter to them, the new ones are as smooth as butter. Just for reference for anyone else reading, I ordered the R4-2Z abec 7 bearings ?as well as belleville washers Robert, That may be one of the best explanations of imaging scale as it relates to PE I've seen, I've read through various explanations of imaging scales and exposure time, but this one just seemed to "click" so thanks! When I'm feeling a little more bold I may extract the PE curve data and play with it in excel as you've described, I definitely see the long wavelength component, but not sure there would be a way to correct for this in a PEC curve as they are typically only one period long, correct? Either way more data and info is always better! I really appreciate you including you're pre/post HP worm data, I'm a visual person and it seems like it would be a great investment. Unfortunately for the time being my imaging camera is a Sony mirrorless (a5100 which is a whole other story, but it wasnt purchased as an astro cam so overall I'm happy its somewhat usable for now) but I do find the idea of higher gain, lower shutter speed and more subs intriguing. Honestly my camera is a big reason why I'm reluctant to mount upgrades piling up - I would really like to get a dedicated cooled astro cam in the nearish future. Derek, That sounds like an offer I can't refuse hah, I will message you shortly!? Brian, I agree :-D? Future Plans: At this point with the significant difference even by hand feel of the bearings, I plan to change out the bearings, add the belleville washers and at the same time switch the RA and Dec worms back to how they were on the first baseline run. I want to see how this can perform, and assuming I am able to work out borrowing the HP worm from Derek, I will do another run using the HP worm and compare. I have to admit, I've really enjoyed imaging several times, but I also really enjoy problem solving and trouble shooting (on a budget of course) something about collecting data and being able to analyze and make sense of it is very satisfying. Thank you everyone for your help thus far, and I look forward to keeping this updated with step by step progress with supporting data! |
Re: Used GM-8 Guiding Help
Derek that's very kind of you :) On Thu, Jan 28, 2021 at 12:07 PM Derek C Breit <breit_ideas@...> wrote:
--
Brian? Brian Valente portfolio |
365 covers, condensation, and Wavy Washer standing water..
¿ªÔÆÌåÓýPreviously ¡°we¡± discussed covers and condensation.. Gun Heating Rods sound like a fantastic solution.. ? Having given away my power supply ¨C like an idiot ¨C and knowing big rain was coming ¨C I finally dismounted my refractor and brought the mount inside.. A few days ago I cleaned and relubed the mount bearings (not to be confused with the drive bearings which still need to be done) and found something ¡°weird¡±.. ? The cylindrical bearings, flat bearings, and thrust washers were essentially pristine.. but the wavy washers were a different story.. They had standing water on them and the lube was quite sticky.. They cleaned up fine, but I thought I would mention it.. Anyone who mostly keeps there stuff setup, might want to check their wavy washers more often than the rest of the mount.. ? Also, the Michael Herman clutch discs were still pristine as well.. A little shiny in spots because I crank my clutches down a lot.. Once I put it all back together, I did play with the mount and figured out I need a whole lot less clutch to make things work, as these clutch discs are either fully slipping or fully engaged.. There is no partially engaged.. Maybe less tightening will help or even fix my Declination backlash issue.. (I haven¡¯t had a chance to try the new PHD2 which is supposed to have improved functions to help with Declination backlash.. ) ? I am glad I put the wavy washers in the ¡°outside position¡± as recommended so the moisture didn¡¯t get anywhere near the flat roller bearings, that¡¯s for sure.. I am more impressed with the G11 every time I touch it.. A really impressive machine.. ? Derek |
Re: Hello from a new user
¿ªÔÆÌåÓýWelcome to the Fun, Brian.. ? :-)) ? Derek ? From: [email protected] [mailto:[email protected]] On Behalf Of brianm
Sent: Wednesday, January 27, 2021 8:07 PM To: [email protected] Subject: [Losmandy_users_io] Hello from a new user ? Hi all.
My wife and I got into this hobby in the mid-80s with a classic orange C8.
After getting a ton of use out if it, both visually and a bit of film-based AP,
a new?10¡± LX50 followed in the late 90s. But life intrudes, and the past
two decades in Dallas and LA put the kebosh on stargazing, for both time and
sky quality reasons. We¡¯ve finally gotten back into it after a move to Utah and subsequent
retirement.? Very
happy to join this group, as well as the Gemini group. Good to ¡°meet¡± you all. ? |
Re: Used GM-8 Guiding Help
¿ªÔÆÌåÓýNick.. ? If you give me your address, you can borrow my extra brass worm to see if you want to install one / if it helps solve the problem.. ? Then you can either buy one from Losmandy and send mine back to me or pay me for mine.. ? Email me directly if you are interested.. ? Derek |
Re: Eastside Heavy Rule - How to Practically Apply Query
¿ªÔÆÌåÓýI move the lower counterweight up or down the shaft depending on which side of the mount things are.. *AND* I find where these points are ¨C before ever turning on the mount ¨C during initial balancing.. ? Doesn¡¯t take much offset from balanced, just ¡°some¡±.. ? With the Gemini II, you also have a balance function that you might like more, but since my configuration never changes, I just find where the weights go once and just put the weights where they go when they need to go there.. ? Derek ? From: [email protected] [mailto:[email protected]] On Behalf Of Terry Pullen via groups.io
Sent: Thursday, January 28, 2021 5:11 AM To: [email protected] Subject: [Losmandy_users_io] Eastside Heavy Rule - How to Practically Apply Query ? Hello Group |
Re: Used GM-8 Guiding Help
Just a few further thoughts on periodic error. See graph below:?
If you start imaging at point B, then in half the worm period, you will get a shift in the image of 2P arc seconds. For your G8 data, P is about 20", and the worm period is 8 minutes. Therefore you will get a star moving by 40" in 4 mins (or 5" in 30 seconds). This is the worst case. If you start at point A, you will only get an image shift of P in half the worm period - for your case this would be 2.5" in 30 seconds. If you're imaging at a scale of 2" per pixel, you should be able to get unguided images OK for 15-30 seconds even with the mount as it is now.? This is ignoring the use of PEC. If you use PEC, then the data in your first figure suggests that P is reduced to only 4 or 5". So with PEC enabled, you would get an image shift of only 1" per minute.? I'm ignoring any high frequency features in the periodic error - if you can get rid of these you should be OK to do some unguided imaging. You can check how long you can go before you get an unacceptable rate of bad frames.? Then you would only need autoguiding if you want to go longer than this. With some of the recent CMOS cameras that are available (like the ASI 071) there are many who are choosing to go to high gain/short exposure time (10-20 seconds) and simply collecting hundreds of frames, and if you choose to go this route you could potentially get rid of autoguiding altogether.? |
Re: Making the most of cloudy winter nights with a new mount and scope
I¡¯ll also add, that my routine for using the AAP with the Gemini 1 is as follows, which might help?
- Power up AAP - Power on Gemini - Focus using AAP (I also have an EAF) - Cold start Gemini (I set up each night) - set location from stored location if cold start lat long incorrect (check mount time is correct UTC no DST) - restart Gemini 1 (if changed location) - connect to mount is AAP - Undertake PA process in AAP and mount bolts - Slew to target with AAP - take preview picture (5 secs) - plate solve and Centre in AAP (just to ensure the target is centred) - start looping and guide process in AAP (I always calibrate every time as I setup each time) - check mount tracking is on (should be automatic) - Start imaging using auto run in AAP. - sit in the warm house and monitor on your phone or tablet! Hope this helps. Took me a while to get a routine that consistently worked with the ASP and Gemini 1. I suspect Gemini 2 isn¡¯t too different. Bryn |
Re: Making the most of cloudy winter nights with a new mount and scope
Join the ASIAIR and ASIAIR Pro user groups on Facebook. Lots of excellent help and assistance. The AAP has really been a game changer for me, getting me imaging whenever the weather allows.
Make sure the epoch on the mount is set to ¡°current¡± not J2000. Took me weeks to figure this out after my AAP would never properly plate solve and Centre targets! The AAP uses know (current) Epoch. Start with Dec and RA aggressiveness of +45 and calibration figures of 500, 300 and 300 for guiding the HM-8 with the AAP, this should give you a reasonable starting point (again, this took me a while to sort and lots of forum surfing!) Back up the AAP SD card immediately. If it corrupts without backup, it¡¯s a bit of a pain to sort out with ZWO by all accounts. I can¡¯t really help with other stuff, but I have been using the AAP with Gemini 1 for 5-6 months now so have experience. There do not seem to be many ASP and Gemini users around? Bryn |
Re: Hello from a new user
Hi Brian, Welcome back to astronomy...we've missed you. But seriously...do have fun!!! Jamey On Thu, Jan 28, 2021, 4:17 AM brianm <bkmiller4463@...> wrote:
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