Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a long time, getting between 0.4 (on very good nights) and 0.9" in RMS, typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I am far more "exposed" to scintillation and seeing effects with the OAG. But is that what this is all about - so that my worse guding is not in fact worse at all.....? I find that my guiding curves (the graph in PHD2) shows what I would call irregular patterns in both DEC and RA, rather than for instance, stable DEC with a slow drift (caused by the PA error), and RA "chatter" caused by variuos PE frequencies. THis makes me think I am chasing seeing. However, increasing the exposure time to 3 sec or higher only results in wors guiding. Best results so far is with 1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns I see would not result in elongaged stars but "only" higher FWHM, as I understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

Just to make sure, did you create a new profile in PHD2 with a guide focal length of 2000??? If not, then PHD2 still thinks your guide scope is 600 mm when it calculates your error in arc-sec. It could be overstating your error.?? I assume you've also re-run your calibration as well, right?? Chances are you've already done both these things, but I just wanted to make sure.?? I also am ready to switch from a 60mm guidescope to an OAG, but have been reluctant to do so since the guidescope has been working very well for me lately.? I'd love to hear what the remedy winds up being.

Best of luck to you,
-Tony

On 9/23/2021 2:35 PM, Magnus Larsson wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a long time, getting between 0.4 (on very good nights) and 0.9" in RMS, typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I am far more "exposed" to scintillation and seeing effects with the OAG. But is that what this is all about - so that my worse guding is not in fact worse at all.....? I find that my guiding curves (the graph in PHD2) shows what I would call irregular patterns in both DEC and RA, rather than for instance, stable DEC with a slow drift (caused by the PA error), and RA "chatter" caused by variuos PE frequencies. THis makes me think I am chasing seeing. However, increasing the exposure time to 3 sec or higher only results in wors guiding. Best results so far is with 1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns I see would not result in elongaged stars but "only" higher FWHM, as I understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

Magnus can you share your guidelogs including a calibration run

On Thu, Sep 23, 2021 at 11:35 AM Magnus Larsson <magnus850@...> wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a
long time, getting between 0.4 (on very good nights) and 0.9" in RMS,
typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was
expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I
am far more "exposed" to scintillation and seeing effects with the OAG.
But is that what this is all about - so that my worse guding is not in
fact worse at all.....? I find that my guiding curves (the graph in
PHD2) shows what I would call irregular patterns in both DEC and RA,
rather than for instance, stable DEC with a slow drift (caused by the PA
error), and RA "chatter" caused by variuos PE frequencies. THis makes me
think I am chasing seeing. However, increasing the exposure time to 3
sec or higher only results in wors guiding. Best results so far is with
1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns
I see would not result in elongaged stars but "only" higher FWHM, as I
understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

--

Brian?

Brian Valente

portfolio

Magnus are these both from the OAG?

It's hard to know what's actually going on with these two guidelogs because you have poor guidestar SNR and you have many lost guidestars throughout your calibration and your guiding. here's a couple examples (guidestar is in yellow, should be a flat line across the top):

Your last run from 9-16 reports a total 0.43" RMS. your polar alignment seems?quite off as all DEC corrections are in one direction. you don't have adaptive backlash compensation on, so that may account for some DEC improvements.?

It would be more helpful to compare your previous separate guiding setup with an OAG run that isn't quite to plagued?with seeing problems

On Thu, Sep 23, 2021 at 12:12 PM Magnus Larsson <magnus850@...> wrote:

Hi!

Here's a guide log fron the 22nd. There are two runs there that are quite typical (the longer ones). And a log with a calibration, also typical.

I've been having lousy weather lately, so a lot of interrupted sessions, and some of the guide logs thatlook strange are due to clouds while I am not attenting the scope.

Do these help?

Magnus

Den 2021-09-23 kl. 20:55, skrev Brian Valente:

Magnus can you share your guidelogs including a calibration run

On Thu, Sep 23, 2021 at 11:35 AM Magnus Larsson <magnus850@...> wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a
long time, getting between 0.4 (on very good nights) and 0.9" in RMS,
typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was
expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I
am far more "exposed" to scintillation and seeing effects with the OAG.
But is that what this is all about - so that my worse guding is not in
fact worse at all.....? I find that my guiding curves (the graph in
PHD2) shows what I would call irregular patterns in both DEC and RA,
rather than for instance, stable DEC with a slow drift (caused by the PA
error), and RA "chatter" caused by variuos PE frequencies. THis makes me
think I am chasing seeing. However, increasing the exposure time to 3
sec or higher only results in wors guiding. Best results so far is with
1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns
I see would not result in elongaged stars but "only" higher FWHM, as I
understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

--

Brian?

Brian Valente

portfolio

--

Brian?

Brian Valente

portfolio

Hi!

Yeah, there are a lot of issues with these - the bad SNR is caused by clouds, basically. I'll get a new calibration and run as soon as the storm calms down and clouds give me a break...then I can even check my PA, that normally is around 1'.

I've got a load of logs, though, and they all are of quite similar quality, except SNR - from above 100 to several hundreds. Still the same RMS.

Best,

Magnus

On 2021-09-23 21:37, Brian Valente wrote:

Magnus are these both from the OAG?

It's hard to know what's actually going on with these two guidelogs because you have poor guidestar SNR and you have many lost guidestars throughout your calibration and your guiding. here's a couple examples (guidestar is in yellow, should be a flat line across the top):

Your last run from 9-16 reports a total 0.43" RMS. your polar alignment seems?quite off as all DEC corrections are in one direction. you don't have adaptive backlash compensation on, so that may account for some DEC improvements.?

It would be more helpful to compare your previous separate guiding setup with an OAG run that isn't quite to plagued?with seeing problems

On Thu, Sep 23, 2021 at 12:12 PM Magnus Larsson <magnus850@...> wrote:

Hi!

Here's a guide log fron the 22nd. There are two runs there that are quite typical (the longer ones). And a log with a calibration, also typical.

I've been having lousy weather lately, so a lot of interrupted sessions, and some of the guide logs thatlook strange are due to clouds while I am not attenting the scope.

Do these help?

Magnus

Den 2021-09-23 kl. 20:55, skrev Brian Valente:

Magnus can you share your guidelogs including a calibration run

On Thu, Sep 23, 2021 at 11:35 AM Magnus Larsson <magnus850@...> wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a
long time, getting between 0.4 (on very good nights) and 0.9" in RMS,
typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was
expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I
am far more "exposed" to scintillation and seeing effects with the OAG.
But is that what this is all about - so that my worse guding is not in
fact worse at all.....? I find that my guiding curves (the graph in
PHD2) shows what I would call irregular patterns in both DEC and RA,
rather than for instance, stable DEC with a slow drift (caused by the PA
error), and RA "chatter" caused by variuos PE frequencies. THis makes me
think I am chasing seeing. However, increasing the exposure time to 3
sec or higher only results in wors guiding. Best results so far is with
1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns
I see would not result in elongaged stars but "only" higher FWHM, as I
understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

--

Brian?

Brian Valente

portfolio

--

Brian?

Brian Valente

portfolio

Though I never had problems with my guide scope (my tracking was probably too bad to notice anyway) when I switched to an OAG for my 12" I never looked back.? At first I had a hard time finding stars but that seems to be resolved, just a matter of practice.? My main gripe is configuring the prism at the center of the long side of the sensor, sometimes I need shims.? I am confident that the OAG gives me the best guiding possible.? After adding a 3:1 timing belt to my OnStep I finally have a system that works OK.? Before, I think the cheap 12 V 0.9 degree steppers were not strong enough, incremental torque wise.? Good to hear you solved your problem, it sounds like there was none.

Hi Magnus

you said

>>>I am still looking for the improvement I was hoping for with an OAG.

I think there may be some misunderstanding about what moving to an OAG will improve

An off axis guider (OAG) is better than a separate guidescope for the following situations/issues:

1. differential flexure. If your guiding results look good, but you still have elongated stars, chances are it's differential flexure caused by the guidescope setup. Often times the physical connections on the guidescope are not as solid or reliable as what you have on the imaging scope (using rings or finderscope attachment, for example).?

2. image scale mismatch - If the image scale on the guidescope is grossly underpowered for your imaging scope. For example, resellers can sell an imaging package of a really long focal length imaging ota and a very short (120mm focal length) finderscope type of guide camera. The result is the guiding scale is not fine enough resolution to adequately guide for the imaging scope, and poor images result. Generally i would not go above 1:4 ratio on these two. Of course with an OAG it is 1:1

3. Generally poor guiding setup - Sometimes people use whatever is available for guidescope or guide camera, and they just aren't the greatest: poor optics, inability to focus, etc. the guiding setup is more forgiving than imaging, but you still need a focused camera and reasonable resolution.?

4. I forgot the last point. Hopefully it will come back to me and i will edit the post.?

If your guiding issues are not covered above, chances are you are not going to benefit much from an OAG.??

On Sun, Sep 26, 2021 at 11:09 AM Magnus Larsson <magnus850@...> wrote:

Hi all!

So yesterday I had a chance to redo my guiding. New calibration, drift align for improved PA and then guided throughout the night. On and off, clouds seems to have disturbed the imaging - everything was not completed in my scheduler. This also means that there are a lot of guiding sessions that are short, messy and terminated. I blame that on the clouds.

You need probably also to know that I do variable stars here, not DSO imaging. This means that there are some short jobs (maybe 10 mins), then slew to another target, and some longer jobs that also are repeated, typically some 30 to 60 mins long (long duration time resolved imaging, this night of SS Cyg, 57 mins long). So the log might look slightly different as compared to a typical DSO log.

Overall, the guiding here was a lot better than what I complained about. However, I'd be happy to hear your reflections on it. As usual, RA is not as good as DEC. There are a few odd DEC movements, where DEC is simply jumping off for a while, then to jump back. No idea what that is. In general, I blame chaotic guding and jumpy SNR on the thin clouds. So I focus my own attention on the more smooth runs, where it might be more a matter of the mount and guiding equipment. Session no 20 is one such. I was watching the whole time, the sky was clear and all went well, then clouds came in, causing some havoc.

Happy to hear your thoughts!

Magnus

Den 2021-09-23 kl. 21:44, skrev Magnus Larsson via :

Hi!

Yeah, there are a lot of issues with these - the bad SNR is caused by clouds, basically. I'll get a new calibration and run as soon as the storm calms down and clouds give me a break...then I can even check my PA, that normally is around 1'.

I've got a load of logs, though, and they all are of quite similar quality, except SNR - from above 100 to several hundreds. Still the same RMS.

Best,

Magnus

On 2021-09-23 21:37, Brian Valente wrote:

Magnus are these both from the OAG?

It's hard to know what's actually going on with these two guidelogs because you have poor guidestar SNR and you have many lost guidestars throughout your calibration and your guiding. here's a couple examples (guidestar is in yellow, should be a flat line across the top):

Your last run from 9-16 reports a total 0.43" RMS. your polar alignment seems?quite off as all DEC corrections are in one direction. you don't have adaptive backlash compensation on, so that may account for some DEC improvements.?

It would be more helpful to compare your previous separate guiding setup with an OAG run that isn't quite to plagued?with seeing problems

On Thu, Sep 23, 2021 at 12:12 PM Magnus Larsson <magnus850@...> wrote:

Hi!

Here's a guide log fron the 22nd. There are two runs there that are quite typical (the longer ones). And a log with a calibration, also typical.

I've been having lousy weather lately, so a lot of interrupted sessions, and some of the guide logs thatlook strange are due to clouds while I am not attenting the scope.

Do these help?

Magnus

Den 2021-09-23 kl. 20:55, skrev Brian Valente:

Magnus can you share your guidelogs including a calibration run

On Thu, Sep 23, 2021 at 11:35 AM Magnus Larsson <magnus850@...> wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a
long time, getting between 0.4 (on very good nights) and 0.9" in RMS,
typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was
expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I
am far more "exposed" to scintillation and seeing effects with the OAG.
But is that what this is all about - so that my worse guding is not in
fact worse at all.....? I find that my guiding curves (the graph in
PHD2) shows what I would call irregular patterns in both DEC and RA,
rather than for instance, stable DEC with a slow drift (caused by the PA
error), and RA "chatter" caused by variuos PE frequencies. THis makes me
think I am chasing seeing. However, increasing the exposure time to 3
sec or higher only results in wors guiding. Best results so far is with
1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns
I see would not result in elongaged stars but "only" higher FWHM, as I
understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

--

Brian?

Brian Valente

portfolio

--

Brian?

Brian Valente

portfolio

--

Brian?

Brian Valente

portfolio

Hi!

Yeah, there are a lot of issues with these - the bad SNR is caused by clouds, basically. I'll get a new calibration and run as soon as the storm calms down and clouds give me a break...then I can even check my PA, that normally is around 1'.

I've got a load of logs, though, and they all are of quite similar quality, except SNR - from above 100 to several hundreds. Still the same RMS.

Best,

Magnus

On 2021-09-23 21:37, Brian Valente wrote:

Magnus are these both from the OAG?

It's hard to know what's actually going on with these two guidelogs because you have poor guidestar SNR and you have many lost guidestars throughout your calibration and your guiding. here's a couple examples (guidestar is in yellow, should be a flat line across the top):

Your last run from 9-16 reports a total 0.43" RMS. your polar alignment seems?quite off as all DEC corrections are in one direction. you don't have adaptive backlash compensation on, so that may account for some DEC improvements.?

It would be more helpful to compare your previous separate guiding setup with an OAG run that isn't quite to plagued?with seeing problems

On Thu, Sep 23, 2021 at 12:12 PM Magnus Larsson <magnus850@...> wrote:

Hi!

Here's a guide log fron the 22nd. There are two runs there that are quite typical (the longer ones). And a log with a calibration, also typical.

I've been having lousy weather lately, so a lot of interrupted sessions, and some of the guide logs thatlook strange are due to clouds while I am not attenting the scope.

Do these help?

Magnus

Den 2021-09-23 kl. 20:55, skrev Brian Valente:

Magnus can you share your guidelogs including a calibration run

On Thu, Sep 23, 2021 at 11:35 AM Magnus Larsson <magnus850@...> wrote:

Hi!

Maybe you in this group can help me understand this:

I'm using a G11 with a C11. I've been guiding with a guidescope for a
long time, getting between 0.4 (on very good nights) and 0.9" in RMS,
typically around 0.6-0.7".

Now I am trying with an OAG. And now I rarely get below 1". I was
expecting better, not worse guiding.

My guidescop is f= 600 mm, on my C11 I have 2000 mm focal length. So I
am far more "exposed" to scintillation and seeing effects with the OAG.
But is that what this is all about - so that my worse guding is not in
fact worse at all.....? I find that my guiding curves (the graph in
PHD2) shows what I would call irregular patterns in both DEC and RA,
rather than for instance, stable DEC with a slow drift (caused by the PA
error), and RA "chatter" caused by variuos PE frequencies. THis makes me
think I am chasing seeing. However, increasing the exposure time to 3
sec or higher only results in wors guiding. Best results so far is with
1 sec exposure.

I have an Atik OAG and a ZMW Asi 174 camera in it.

And: images are good. Not worse than before at least... But the patterns
I see would not result in elongaged stars but "only" higher FWHM, as I
understand it.

Any ideas on this? What are your experiences from using OAGs?

Magnus

--

Brian?

Brian Valente

portfolio

--

Brian?

Brian Valente

portfolio