Just when you think you know what you're doing... - Forums

Topic starter

May 10, 2023 · Edited: May 10, 2023

Just when you start to think you know what you're doing, the universe smacks you around a little to keep you grounded. First off, this isn't a great image of M106. It's what I could manage with too few subs. It's a total of about 80 minutes of 5-minute exposures, so few that I just about didn't bother. I was so discouraged that I didn't even take darks, flats, etc. Due to some poor decisions on my part last night, my guiding was hit or miss for much of the night, and I ended up with a lot of subs that were completely unusable. Then when I finally got things straightened out, Mother Nature decided to defy the weather forecast and send in the clouds. So I ended up with three additional hours of clouded-out subs (I was sleeping by that time). I'm a little surprised that I was able to get even this image from last night's effort. I didn't bother contemplating adding more time to this in subsequent evenings because we're going to have lousy weather for the next several days, at least. And it seemed like it might make more sense to just start over fresh, you know?

At least three lessons were reinforced for me last night, regarding guiding:

Don't expect guiding to work well if you haven't built the dark library for your guide camera.
When you're using an OAG, tell N.I.N.A. to stop guiding while autofocusing is in progress.
Make sure your guide camera/OAG is properly focused.

Oh, and lesson 4 was that if you have a dew shield and dew heater, use them! Doh!

I shot this using my C8 with the Starizona SCT Corrector, making it about a 1450 mm f/7 configuration. I'm still getting my feet wet with the C8--it's more challenging to shoot with than my SW Esprit 100ED refractor. I was using off-axis guiding with ZWO OAG and an ASI290MM mini guide scope. The main camera is an ASI533MM Pro, and the whole works sits on an iOptron GEM45 mount on a concrete pier. I shot it in mono using LRGB filters and then processed it in PixInsight.

Helpful Insightful Respectful Engaging Supportive

A. Wegdan

May 11, 2023

I know exactly what you mean

Claudio Tenreiro

May 11, 2023

I know exactly what you mean

+1,

Jerry Gerber

Frequent contributor

May 11, 2023 · Edited: May 11, 2023

I haven't built a dark library for my guide camera (but I may in the future if problems occur) and my guiding is between .4" and .6" on both the RA and DEC axis and has been stable throughout the night.

I also have the Esprit 100 ED and the Edge HD 8. In my limited experience, I have found that seeing conditions out of my control affect guiding more than any other factor. Assuming polar alignment is excellent, the guide camera's focus, calibration step, max RA and max DEC durations are set properly and the gain isn't too high or too low, the other variables are seeing and focal length. I'm finding guiding much easier with a 50mm guide scope on my refractors than I am with the OAG guider at 2032mm or 1422 with the Edge. The other night, using the OAG and the Edge 8 at f10, I could not even find a guide star, the first time that happened.

Helpful Insightful

Dave Ek

Topic starter

May 11, 2023

Jerry Gerber:
I haven't built a dark library for my guide camera (but I may in the future if problems occur) and my guiding is between .4" and .6" on both the RA and DEC axis and has been stable throughout the night.

I also have the Esprit 100 ED and the Edge HD 8. In my limited experience, I have found that seeing conditions out of my control affect guiding more than any other factor. Assuming polar alignment is excellent, the guide camera's focus, calibration step, max RA and max DEC durations are set properly and the gain isn't too high or too low, the other variables are seeing and focal length. I'm finding guiding much easier with a 50mm guide scope on my refractors than I am with the OAG guider at 2032mm or 1422 with the Edge. The other night, using the OAG and the Edge 8 at f10, I could not even find a guide star, the first time that happened.

Yes, I've noticed that with my C8 and OAG that guide stars can sometimes be a bit scarce. Glad it's not just me. I *do* know that some combination of building the dark library and tweaking my guide camera focus brought my guiding back to life. Building the dark library for PHD2 only takes a minute or two, thankfully.

Well Written Concise Supportive

Nick Grundy

May 11, 2023

Jerry Gerber:
seeing conditions out of my control affect guiding

I get the same here in North Bay. same setup on one night could average .2-.3", and the next night I manage only .5"

I've steadily upped my guide scopes though to counter it. Can't yet tell if it's working (I think it is). I know they say it's no necessary, but I even used my asi533 for guiding the other night in order to get a better field.

Frank Alvaro

May 11, 2023

I hadn't heard of a dark library for the guide camera until I read this post, and upon investigation I've found that the ASIAir allows one to be built. However, I cannot find any explanations of how and why this works… can anyone shed some light on this please?

Well Written Engaging

Dave Ek

Topic starter

May 11, 2023 · Edited: May 11, 2023

Frank Alvaro:
I hadn't heard of a dark library for the guide camera until I read this post, and upon investigation I've found that the ASIAir allows one to be built. However, I cannot find any explanations of how and why this works... can anyone shed some light on this please?

I can't speak to the AA, but I can say that PHD2 practically insists that you build a dark library when you first set up a profile.

If for no other reason, having a dark library helps to ensure that the guiding software doesn't mistake a hot pixel for a star.

Well Written Concise

Jerry Gerber

Frequent contributor

May 12, 2023

Dave Ek:
Frank Alvaro:
I hadn't heard of a dark library for the guide camera until I read this post, and upon investigation I've found that the ASIAir allows one to be built. However, I cannot find any explanations of how and why this works... can anyone shed some light on this please?

I can't speak to the AA, but I can say that PHD2 practically insists that you build a dark library when you first set up a profile.

If for no other reason, having a dark library helps to ensure that the guiding software doesn't mistake a hot pixel for a star.

When I watch the ASIAIR Plus find guide stars, I can see which ones it's choosing, it doesn't seem likely that it could mistake a hot pixel for a star, but maybe it can.

I am going to a Bortle 1-2 site this weekend, and the sky and weather conditions are looking good. It will be very nice to get out of Bortle 7 skies not just for imaging, but for my own peace of mind!

Dave Ek

Topic starter

May 12, 2023

I am going to a Bortle 1-2 site this weekend, and the sky and weather conditions are looking good. It will be very nice to get out of Bortle 7 skies not just for imaging, but for my own peace of mind!

I live in Bortle 4, so I guess I'm spoiled. Except for the fact that it's been snowing here all day...

Well Written Respectful

Jerry Gerber

Frequent contributor

May 12, 2023 · Edited: May 12, 2023

Dave Ek:
I am going to a Bortle 1-2 site this weekend, and the sky and weather conditions are looking good. It will be very nice to get out of Bortle 7 skies not just for imaging, but for my own peace of mind!

I live in Bortle 4, so I guess I'm spoiled. Except for the fact that it's been snowing here all day...

No snow here in San Francisco, just lots of coastal fog. Mark Twain said the coldest winter he ever spent was a summer in San Francisco.

Well Written Respectful

Nick Grundy

May 12, 2023

Dave, I just found another fundamental to add to your list….

when you balance your scope on an equitorial mount, take off the dust cap first!

I spent 20 minutes dialing in the perfect balance in all 3 axis, ready to get some crazy good guiding tonight. Then realized it was all off once I got it out there. Dustcaps might not weigh much, but at the end of a 130mm refractor it has a big impact on the balance.

Well Written Helpful Insightful Concise Engaging

Scott Badger

May 12, 2023 · Edited: May 12, 2023

Jerry Gerber:
No snow here in San Francisco, just lots of coastal fog. Mark Twain said the coldest winter he ever spent was a summer in San Francisco.

I'm very fortunate to have Bortle 3 and no visible artificial lighting....except for my daughter's bedroom window, that is....so many lights on, it looks like a lighthouse beacon! Ha! No fog, but lately plenty of smoke from the forest fires in Alberta.....2,000 miles away!

My guiding also goes hand in hand with the seeing, and my seeing is bad when it's good.... When I had a CGEM, I really obsessed over the guiding because the mount desperately needed it, but I hated that I spent most of my time under the stars staring at a graph on my laptop, so when a new mount (CEM70) solved half the battle, I decided to not worry about it anymore and start enjoying starry nights again. That said, it'd be nice to not compound bad seeing with bad guiding, but efforts to improve the results haven't been very successful and even if I really bore down on it, the majority of my imaging time (if it's clear all night) is while I'm in bed and the seeing can be very dynamic..... What would be really great is an AI PHD2 plug-in, that's a job I'd gladly hand over to the robots!

Another for the list, after pausing imaging to re-center, focus etc., remember to hit start again before going to bed......

Cheers,
Scott

Engaging

Dave Ek

Topic starter

May 12, 2023

Nick Grundy:
Dave, I just found another fundamental to add to your list....

when you balance your scope on an equitorial mount, take off the dust cap first!

I spent 20 minutes dialing in the perfect balance in all 3 axis, ready to get some crazy good guiding tonight. Then realized it was all off once I got it out there. Dustcaps might not weigh much, but at the end of a 130mm refractor it has a big impact on the balance.

Been there, done that--with the dust cap, the dew shield, you name it.

Roy Hagen

May 12, 2023

Been there, done most of that😢 and a few more f…ups
Just like being seventeen again
Immortal world champion of everything, and suddenly reality bites🤬

James (Jim) Poulette

May 16, 2023

Man, I've got light years ahead of me before I even begin to think I know what I'm doing.

Those are good lessons for everyone. Thanks!

George Hatfield

May 17, 2023

I have a Celestron 8" Edge HD with an ASI533 imaging camera, a Celestron OAG, and an ASI174 guide camera. I've done a fair amount of refractor imaging, and this is my first foray into long focal-length imaging, mainly of galaxies. I have never used a dark library for my guide camera, and I don't think it is very common to use one. I don't see the advantage, especially for low-noise CMOS sensors. Your problems are probably not due to the lack of a dark library. Of course, I use darks, bias, and flats to calibrate my images, and I think that is absolutely essential, even though some claim the 533 does not need darks.

I use the ASIAIRplus to control my imaging sessions, and it automatically stops guiding during focusing routines. I accept the fact that a NINA system has greater capabilities, but the AA+ makes everything so simple it is a good trade-off for me.

If you are using an OAG, the distance from the prism to your guiding sensor should be the same as from the prism to your imaging sensor. The same backfocus applies. Once you have your imaging sensor in focus, followed by the guiding sensor, leave the latter alone. You should not have to fool with the guiding sensor focus again when you refocus on your main sensor. I use autofocusing with the AA+ and often do it every 30 minutes. It is easy and automatic.

Finding a guide star, especially when using a reducer on the 8" SCT, can be difficult. First, you have a reduced image circle. For the 8" edge, the imaging circle goes from 42mm to 26.7mm. So even with a small imaging sensor like the 533, you are trying to guide with stars on the outer edge of the imaging circle… an area that is notorious for distorted stars. James Lamb has several Youtube videos on using Stellarium to find guide starts. I use his technique, and I have always been able to find a suitable guide star if Stellarium shows one is there. I typically use 4 or 5-second exposures for guiding. I know this is long, but this exposure gives a good star intensity for guiding, and I get better results.

Helpful

Dave Ek

Topic starter

May 17, 2023

George Hatfield:
I have a Celestron 8" Edge HD with an ASI533 imaging camera, a Celestron OAG, and an ASI174 guide camera. I've done a fair amount of refractor imaging, and this is my first foray into long focal-length imaging, mainly of galaxies. I have never used a dark library for my guide camera, and I don't think it is very common to use one. I don't see the advantage, especially for low-noise CMOS sensors. Your problems are probably not due to the lack of a dark library. Of course, I use darks, bias, and flats to calibrate my images, and I think that is absolutely essential, even though some claim the 533 does not need darks.

I use the ASIAIRplus to control my imaging sessions, and it automatically stops guiding during focusing routines. I accept the fact that a NINA system has greater capabilities, but the AA+ makes everything so simple it is a good trade-off for me.

If you are using an OAG, the distance from the prism to your guiding sensor should be the same as from the prism to your imaging sensor. The same backfocus applies. Once you have your imaging sensor in focus, followed by the guiding sensor, leave the latter alone. You should not have to fool with the guiding sensor focus again when you refocus on your main sensor. I use autofocusing with the AA+ and often do it every 30 minutes. It is easy and automatic.

Finding a guide star, especially when using a reducer on the 8" SCT, can be difficult. First, you have a reduced image circle. For the 8" edge, the imaging circle goes from 42mm to 26.7mm. So even with a small imaging sensor like the 533, you are trying to guide with stars on the outer edge of the imaging circle... an area that is notorious for distorted stars. James Lamb has several Youtube videos on using Stellarium to find guide starts. I use his technique, and I have always been able to find a suitable guide star if Stellarium shows one is there. I typically use 4 or 5-second exposures for guiding. I know this is long, but this exposure gives a good star intensity for guiding, and I get better results.

Your experiences pretty much line up with mine. N.I.N.A. will stop guiding during autofocusing if I tell it to, which seems to make sense. PHD2 practically insists that i create a dark library for my guide camera, and will do so automatically for me in just a couple minutes. And thanks for the tip on guide stars--I'll check out the videos.

Well Written Respectful