Prime Focus Test

[Tamtarn]

I decided to try prime focus for the very first time last night.

Using my Pentax ist DL and Skywatcher 8" f5 Newt on a EQ5 mount with dual axis drives.

I researched on how to mount my camera and found there were issues of not being able to achieve focus using the R & P focuser and the Newt. After a lot of pondering on what to do I decided to improvise by unscrewing the bottom off the 1.25 eyepiece adapter and using this with the T mount as a camera adapter

OK I connected the camera to the focuser and because of the bright moonlight I decided to test focus and our polar alignment on star images.

I chose beta centauri looked into the view finder on the camera and focused it. Took one shot 30sec ISO 800 on the LCD screen it looked reasonable. At this stage I was just pleased I had something on the image.
Moved to aplha centauri took 4 shots with various times and ISO settings. I noticed there was fog rolling in so I took the camera inside put the shots on the PC and was reasonably happy with the result.

To be quite honest I didn't know what to expect with the focus and tracking. I'm pleased with my first tryout and hope I'm on the right track. I know I've got a long way to go to get it right. I have about 8mm of infocus left but I'm not sure if it will be enough for DSO's If not I will invest in a low profile focuser. I won't know until we have suitable conditions to try it out again.

By the way would the glow around the star come from the fog reflecting or the camera settings.

1. beta centauri .......... 45sec ISO88

2. alpha centauri ......... 60 sec ISO 800 ( I think 45sec would be have been better )




Any comments or suggestions welcome

David

[gbeal]

Looks good, very good, and if you have 8mm up your sleeve, even better.
Fog may have contributed, but there looks like a bit of vignetting there as well. Nothing a decent flat field won't fix though.
Try something bright next time, like Omega Cent, you will be surprised. Shoot a heap at something like 60 secs, and keep the exposures such that your tracking gives round stars. If your polar alighment is better than most maybe try longer times.
Welcome to the frustrating world of astrophotography.
Gary

[Astroman (Andrew Wall)]

Good test images there David, well done, your on your way. The foggyness looks atmospheric to me, but you will need to try on several nights to see if it is an effect of the camera or not.

[EzyStyles (Eric)]

very nice test shots david. the haze around the star looks like fog to me and we have been experiencing bad foggy weather lately in melb. keep it up

[Tamtarn]

Thanks guys for your favorable comments.

Gary - I'll be wrapped if that extra 8mm I have does the job. Will give OC a try next time.

Andrew and Eric - If the sky glow is the result of the fog as you suggest then I look forward to the next time conditions are favorable to try some DSO's.

[gbeal]

Originally Posted by Tamtarn

Thanks guys for your favorable comments.

Gary - I'll be wrapped if that extra 8mm I have does the job. Will give OC a try next time.

David,
and if the extra 8mm doesn't quite do it, there is a few other tricks you can pull out of the bag, shifting the primary forward being one of them.
Gary

[Astroman (Andrew Wall)]

On my Skywatcher 8" F6 I didnt need to move the primary forward, I just had a low profile focuser (JMI NGF-DX3) which did the job perfectly.

[bluescope]

Good start David and you didn't spend a cent on adapters etc as per our previous communication . Keep it up.

Cheers.

[ballaratdragons (Ken)]

WOW David, those main stars are so crisp!!! That's something a Toucam can't do.

As for the foggy glow, it could also possibly be very slight dew on the 2ndry mirror, or Primary mirror..

Looking forward to your 1st DSO's

[Tamtarn]

Originally Posted by bluescope

Good start David and you didn't spend a cent on adapters etc as per our previous communication . Keep it up.

Cheers.

Lucky wasn't I Steve Hope it works on DSO's

Originally Posted by ballaratdragons

WOW David, those main stars are so crisp!!! That's something a Toucam can't do.

As for the foggy glow, it could also possibly be very slight dew on the 2ndry mirror, or Primary mirror..

Looking forward to your 1st DSO's

Hey you're probably right there Ken. When we brought the scope inside we noticed the primary was just dewing up a little.