Blurry stars between shots

[04Stefan07]

Hello all!

I was having issues with some blurry stars the other night. I am not sure if it could be my focuser, guideing or my mount tracking. Sell below what I run.
- HEQ5 Pro
- ES102 APO with ZWO EAF (pretty much this setup file:///D:/Installation%20of%20the%20ZWO%20EAF %20on%20an%20Explore%20Scientific%2 0ED102%20(1).pdf)
- ZWO 60mm Guidescope with QHY5L-II Mono
- Sequence Generator Pro

I took apart my EAF and reattached it to make sure there is no play or lose parts. I had a similar issues on my previous setup which was a C8 with the same guidescope and camera.

I have attached three consecutive photos of my target. You can see its sharp and in focus, then out of focus then back to normal. Then later on it would lose focus and never go back. I had to stop the sequence and change it manually. Also with Sequence Generator Pro I was using the auto focus feature and I could never get the U shape graph when trying to focus. Most of the time it would time out and go back to the best previous position.

I never liked the tube rings and the screws on the guidescope, I feel they never snug the tube properly. Is there something I can test or try that someone can suggest?

Would I need a new guiding package? Is my EAF not focusing correctly or is my mount not trackin right?

[michael8554]

I suggest you take a number of images with the focuser locked solid.

Is your cooled camera fogging up?

There is star elongation too, which is probably guiding - if a series of short exposures all have round stars then guiding is too blame.

Michael

[04Stefan07]

18 minutes ago, michael8554 said:

I suggest you take a number of images with the focuser locked solid.

Is your cooled camera fogging up?

There is star elongation too, which is probably guiding - if a series of short exposures all have round stars then guiding is too blame.

Michael

Cooled camera should be ok, I have a dew strap attached to it which is always on. Yeah short exposures when I was focusing look to be fine.

A few others suggested guiding too. I might have to rethink my guiding package. It could be something as simple as seeing conditions that night but I got a feeling it's some sort of flexure at work here.

[michael8554]

8 hours ago, 04Stefan07 said:

Yeah short exposures when I was focusing look to be fine

As were your initial long exposures, but they went out of focus on subsequent exposures. 

So it's important to take a series with the focuser locked tight.

If stars are in focus then you can assume guiding isn't to blame and you can investigate focuser creep as the cause  on the longer exposures. 

That focus difference may only be due to microns of creep. 

Michael 

[04Stefan07]

Alright so I had success last night!

A few things I did before the session

- Removed the guidescope from the rings, re-sat it and made sure the screws were nice and tight
- Checked that the guide camera was sitting nicely snug with no play
- Reinstalled PHD2 as it stopped working and re-calibrated
- Set up auto focus properly in SGP

All looks to be much better now and getting really sharp images.

[michael8554]

4 hours ago, 04Stefan07 said:

Set up auto focus properly in SGP

What did that involve Stefan, none of the other steps addressed the focus creep? 

Michael 

[04Stefan07]

6 minutes ago, michael8554 said:

What did that involve Stefan, none of the other steps addressed the focus creep? 

Michael 

I followed this fantastic tutorial on how to setup auto focus in SGP.

Once I did that I had really sharp stars. I was trying to notice if there was a bit of backlash or play on the focuser but I couldn't really tell.

Check these out.

https://www.youtube.com/watch?v=s8xc1DBbHT0&t=94s

https://www.youtube.com/watch?v=3kjeTHDHnE4&t=248s