First Guided Astrophoto Session, All Set Up Right, Forgot About Dew..

[cathalferris]

After years as a visual astronomer, mostly due to budgetary concerns, I finally started down the slippery slope of "proper" astrophotography. I've had a Celestron Onyx 80ED f6.2 scope for a while, as well as an IKI 70mm ED f6 that I use as a travel scope. I bought myself a Christmas present of a Celestron AVX mount after selling off my LXD75 the previous year to part-fund my 12" dob.

The first clear nights that I got after the New Year, I tried the video astronomy thing with a 6" newt that I got recently, and that's pretty amazing. Seeing mag 16 galaxies with exposures of 10 sec is definitely nifty! But, it would be nice to have half-decent shots to use as desktop backgrounds and to print off as pics around the house, so I tried using my Canon through the 80mm scope and on the AVX. I was a little disappointed to see just how much periodic error I had in the mount - I was trailing in half of my exposures at 60 sec, better than the half trailed at 30 sec with the LXD that I had. I knew that I'd have to go down the guiding route..

So, I was trawling through the local online ads and I saw a Skywatcher Synguider for sale, I made a lowish offer and it was accepted by the seller.. I picked it up earlier this evening and lo and behold the skies cleared when I got back. I had also purchased an L-bracket for putting the camera on the AVX and I figured out this evening that I could actually mount both of my refractors on the AVX using the l-bracket and a spare tripod head that I had lying around. After a dry run using a Hubble artificial star indoors, I took the setup outdoors and went through the alignment and setup.

I figured I'd give the autoguider a afairly difficult task and test things out, so I picked 5 minute exposures on M51, as it should give me a nice pretty result in the subs. All set up, apparently guiding away grand, and I left it to its devices. I was a little worried about differential flexure as my Rube Goldberg dual mount was definitely not something that I would recommend to others but it was a nice proof of concept to see if it's worth my investing in a proper dual saddle with aiming device. There was plenty of advice for how to use the Synguider properly, things like turn down the aggressiveness of the auto calibration and what numbers to get for brightness and noise and the like. It was very interesting to watch the corrections going on live on the little screen.

After an hour and a half in the freezing cold, not touching the setup for fear of moving something and ruining my alignment, I had had enough of the cold. Taking a quick scan through the exposures before I packed everything up, I was very happy to see that there were lovely round pinpoint stars to be seen on the camera lcd, as well as lovely well defined spiral arms in M51 itself. As I scanned through the 30 or so exposures I saw that M51 got fainter and fainter and much less distinct.. At that stage I took a look at the objective only to see a layer of ice across the glass.. I had completely forgotten to pull the dew shield out fully and  it had slipped down over the exposures, allowing dew to settle on the glass and it froze solid, making it hard ot et anything on the camera!. So, I have about 3 subs to play with for my night's endeavours. Mildly frustrating, but overall I'm well chuffed with how things worked out from a technical point of view. Not a waste of time with the learning involved!

All that remains now is to see if I can salvage anything from the blurry frames, and then to wait for another clear night to do it all again, this time with a decent dew shield and possibly a heater strip or two..

When I get the pics from the camera, I'll add to this thread later on tomorrow.

[Pompey Monkey]

After years as a visual astronomer, mostly due to budgetary concerns, I finally started down the slippery slope of "proper" astrophotography. I've had a Celestron Onyx 80ED f6.2 scope for a while, as well as an IKI 70mm ED f6 that I use as a travel scope. I bought myself a Christmas present of a Celestron AVX mount after selling off my LXD75 the previous year to part-fund my 12" dob.

The first clear nights that I got after the New Year, I tried the video astronomy thing with a 6" newt that I got recently, and that's pretty amazing. Seeing mag 16 galaxies with exposures of 10 sec is definitely nifty! But, it would be nice to have half-decent shots to use as desktop backgrounds and to print off as pics around the house, so I tried using my Canon through the 80mm scope and on the AVX. I was a little disappointed to see just how much periodic error I had in the mount - I was trailing in half of my exposures at 60 sec, better than the half trailed at 30 sec with the LXD that I had. I knew that I'd have to go down the guiding route..

So, I was trawling through the local online ads and I saw a Skywatcher Synguider for sale, I made a lowish offer and it was accepted by the seller.. I picked it up earlier this evening and lo and behold the skies cleared when I got back. I had also purchased an L-bracket for putting the camera on the AVX and I figured out this evening that I could actually mount both of my refractors on the AVX using the l-bracket and a spare tripod head that I had lying around. After a dry run using a Hubble artificial star indoors, I took the setup outdoors and went through the alignment and setup.

I figured I'd give the autoguider a afairly difficult task and test things out, so I picked 5 minute exposures on M51, as it should give me a nice pretty result in the subs. All set up, apparently guiding away grand, and I left it to its devices. I was a little worried about differential flexure as my Rube Goldberg dual mount was definitely not something that I would recommend to others but it was a nice proof of concept to see if it's worth my investing in a proper dual saddle with aiming device. There was plenty of advice for how to use the Synguider properly, things like turn down the aggressiveness of the auto calibration and what numbers to get for brightness and noise and the like. It was very interesting to watch the corrections going on live on the little screen.

After an hour and a half in the freezing cold, not touching the setup for fear of moving something and ruining my alignment, I had had enough of the cold. Taking a quick scan through the exposures before I packed everything up, I was very happy to see that there were lovely round pinpoint stars to be seen on the camera lcd, as well as lovely well defined spiral arms in M51 itself. As I scanned through the 30 or so exposures I saw that M51 got fainter and fainter and much less distinct.. At that stage I took a look at the objective only to see a layer of ice across the glass.. I had completely forgotten to pull the dew shield out fully and  it had slipped down over the exposures, allowing dew to settle on the glass and it froze solid, making it hard ot et anything on the camera!. So, I have about 3 subs to play with for my night's endeavours. Mildly frustrating, but overall I'm well chuffed with how things worked out from a technical point of view. Not a waste of time with the learning involved!

All that remains now is to see if I can salvage anything from the blurry frames, and then to wait for another clear night to do it all again, this time with a decent dew shield and possibly a heater strip or two..

When I get the pics from the camera, I'll add to this thread later on tomorrow.

Nice write-up!

Welcome to the usually wonderful, but regularly frustrating, world of imaging! There are so many factors than can bite you in the behind when you least expect it, but the dificulties, at least for me, make it all the more rewarding when it comes together.

[cathalferris]

Actually turned out quite a bit better than expected for the conditions. There was a fair bit of noise, and I think that my flattener isn't exactly suited to the scope. Still, happy enough with this.

DSS registered and stacked at 70% level, level adjust in PS CS2. I'll have a go later on at a process and stack using IRIS.

(flickr link)

[JohnSadlerAstro]

Hi,

I had the same dew problem with my DSLR, though I wasn't up late enough for it to ice over! I found that using a hairdryer between subs to keep the lens glass warm kept the dew away. All so long as any neighbours don't mind the periodic whirring!

John

[StargeezerTim]

I feel your pain! 

[RSM]

That's just the way it goes sometimes. Setting up this evening, I got my alignment bang on perfect first time of asking. Set everything up, focus, right field of view for the image I wanted, sorted the guiding. Put the home made dew shield on and twisted the whole set up....