Plate Solving issue with Sharpcap Pro

[mhb1989]

I am new to this and trying to do EAA. Had a 9.25 inch scope but decided to use a smaller/faster one so I could plate solve/center easily. So now I have on a permanent pier an AP 1100 go to mount, a Televue NP 101 (4 inches) - my goal tonight was to polar align using sharpcap and then look at stuff but it turned out to be the worst night ever which is too bad as it was SOOOO clear!

First I tried the polar alignment tool -it plate solved in like 2 seconds and worked great (and it wasn't even really that dark yet). I was optimistic. I wasn't sure what you do to change the up/down but since I managed an "excellent" I figured that was good enough. Then I slewed to M57. it wasn't there and I could see visually that it was off a bit.

Tried to plate solve/resync so I could SEE m57. Spent 2 hours trying -used between 2-4 second exposure, kept adjusting the gain -sometimes it would say "only found 15 stars, increase gain" and then I would change it by a small amount and it would either not give an error or say "too many stars" though it was super close. I went between 150-400 gain over and over but could not get it to plate solve/sync. NOT ONCE. I'm ready to cry -how can I see anything to live stack if I can't center the object of even have it in the field of view (which it was not).I must be doing something wrong or have some setting wrong.

Therefore could not center any object to look at it - not m13, not m92. With a 4 inch scope I didn't think I'd have this issue like with the celestron. on the screen (I have a big monitor) I could see 100 stars but sharpcap could "only" see 7. I feel like I'm doing something very basic wrong.
Also, since I"m on a permanent pier and did an excellent polar alignment, why would the pointing be this off?

[admin]

Hi,

first let's check the polar alignment procedure... Once you advance to the adjustment stage of the alignment, you are meant to use the altitude and azimuth boths/screws/adjusters of the mount to make the corrections needed to bring the error amount down. Hopefully that's what you were doing. If you were using the normal mount movement controls to make the adjustments then you weren't actually adjusting your polar alignment, which could have remained significantly off...

Now onto the next stage - issues with plate solving. It would be good to know which plate solving software you were using, as the adjustments needed differ for Astap compared to Astrotortilla/ASPS/Ansvr etc. If you are using Astrotortilla or ASPS/Ansvr then try reducing the 'sigma' setting in the plate solving settings a bit - that makes it detect more stars. Another relatively common issue is that if you have used the display stretch function in SharpCap to brighten stars and the target, that can make you think the stars are easily visible when in fact they aren't in the raw (unstretched) image. Still, an exposure of 2 to 4s and relatively high gain should usually work.

If you have the SharpCap log saved during the session and can share it here then I can investigate further what might have been going on with the plate solving. Even better would be one or two saved frames from the camera (captured with the 'snapshot' button) as I can assess those directly.

thanks,

Robin

[mhb1989]

Thanks Robin! I was hoping you'd help me
I was using ASTAP and the D50 database.
I have to figure out how to do the log thing - are my basic settings correct? It's just odd as visually I could see a million stars as it was super clear - I would move the gain up and it might say "too many stars" and back it off by 10 and it was say too few.

[mhb1989]

And yes, I did not use the keypad - I used the actual azimuth knobs to adjust and the altitude thing.

[mhb1989]

Ugh -I forgot to change the focal length so that may the culprit -will try again tonight and report back!

[admin]

Hi,

yes, the wrong focal length is worse than no focal length at all... With the wrong length it just won't work, with no focal length it will get there in the end.

Good luck this time around

cheers,

Robin