8 replies to this topic

[Jure_13]

Took me four nights to get enough data with the IC 1848. OIII with the full moon in the sky is not such a good idea as it turned out. This was my second SHO imaging session with the new ASI2600MM Pro. I love it, it's such a great camera! 

 

- ST Optics 60mm APO F/6

- SkyWatcher EQ-6
- ASI2600MM Pro
- ZWO SHO filters
- ZWO EWF
- Gain: 100
- Temp -5
- AsiAir Pro imaging + guiding
- 26 x 600 sec Hα
- 24 x 600 sec SII
- 25 x 600 sec OIII
-  5 x 900 sec OIII
- 30 x flat Hα, SII, OIII
- 50 x bias
- 30 x dark

 

 

Larger version here: https://www.astrobin.com/31zj9m/0/

 

I'm having some trouble with elongated stars in N-S direction when the mount is getting low west of the meridian at high DEC. According to AsiAir Pro my PA is 10" or so, the Guide log says 1'. It's repeatable and I think it's not flexure. I really have no clue what is going on. True, seeing is more or less really bad, but I got elongated stars with a 15 min exposure even when the RMS was 1" and without any obvious spikes. 

 

I'm setting up a mini PC with full PHD2 to try and troubleshoot. With so few clear nights I really don't want to discard half of my frames! 

 

Talking about a learning curve! First to do everything right outside to get decent frames, then comes the processing! Sometimes my head hurts!   I don't want to touch PI until I am more confident and know what I'm actually doing most of the time. APP is very kind to a novice like me, so I'm grateful for that. And it does a great job, too. 

Edited by Jure_13, 28 January 2022 - 05:42 AM.

[ChiTownXring]

Most mounts that don't cost an arm and a leg will most likely have trouble with a 15 min exposure. I would experiment making sure your are balanced and polar aligned perfectly and that your guiding is good then start with a 2 min exposure and check for star shape if it's good then increase by 1 min then rinse and repeat until you find a good exposure time for your equipment with a good star shape. From what I have seen most that have a decent mount and good guiding shoot 5 min exposures with good success. Also for what its worth I have tweaked my setup and can guide at 0.15 - 0.25 RMS and still only shoot 5 min subs..

Edited by ChiTownXring, 28 January 2022 - 11:47 AM.

[acrh2]

 

I'm having some trouble with elongated stars in N-S direction when the mount is getting low west of the meridian at high DEC. According to AsiAir Pro my PA is 10" or so, the Guide log says 1'. It's repeatable and I think it's not flexure.

Why do you think that it's not flexure?

You can easily tell that it is or isn't by running a few subs without dithering. 

[Jure_13]

Most mounts that don't cost an arm and a leg will most likely have trouble with a 15 min exposure. I would experiment making sure your are balanced and polar aligned perfectly and that your guiding is good then start with a 2 min exposure and check for star shape if it's good then increase by 1 min then rinse and repeat until you find a good exposure time for your equipment with a good star shape. From what I have seen most that have a decent mount and good guiding shoot 5 min exposures with good success. Also for what its worth I have tweaked my setup and can guide at 0.15 - 0.25 RMS and still only shoot 5 min subs..

I will try that, thank you! Yesterday I fired up NINA and PHD2 for the first time just to see what was up and even a 15 min exposure was, well, relatively good. Much better than before and will go from here. Shorter exposures until I get nice, round stars as you suggested. I think one of the reasons was my calibration. It was done up north instead at app. 0 DEC as PHD2 guide suggests. 

 

How did you tweak your mount if I may ask? My mount is really old, from 2005, but rarely used until now. 

[Jure_13]

Why do you think that it's not flexure?

You can easily tell that it is or isn't by running a few subs without dithering. 

I did that a while ago and stars in each frame were in exactly the same spot. I have done some cable management since and you are right, it could be flexure in certain mount positions. I will check at the same spot I was having problems. But you know how it is, clear nights are so rare and... 

[terry59]

How is the guide scope mounted?

[Jure_13]

Terry, it's a ZWO mini guidescope 30/120 with a single wide-ish bracket, attached to a finder shoe with two screws which itself is attached to the main scope with two screws. I use ASI120MM for guiding.

 

ZWO finder scope: https://www.teleskop...SI-Cameras.html

Finder base: https://www.teleskop...s---Deluxe.html

 

I also make sure the dew heater cable is not dragging the scope. It's very  lightweight and small. I even bought a two ring bracket, the smallest I could find and it's still too wide for the little guide scope. 

[terry59]

That is a potential source of flexure. If you can mount it on top of the scope secured buy two rings it would be more firmly secured

[Jure_13]

Will do, thanks for the advice!