Bubble Nebula - 1 Sep 2013

[orly_andico]

This is a cropped image. 7 x 1200 seconds (2 hours 20 minutes), AT90EDT with Orion non-reducing flattener, QHY8, Baader 7nm H-a filter. Guided with a Meade DSI and Meade 60mm f9 guide scope.



Conditions were very cloudy last night. Had to throw away 3 subs due to clouds (and at 20 minutes per sub.. painful).



Also the Bubble Nebula is low in the north, I don't think it ever gets beyond 30 degrees above the horizon at our latitude. Guiding close to the pole is also more.. problematic. I was getting about 0.3 pixel RMS (about 1" RMS guiding) which is pretty bad.. but since my guide scope image scale is about the same as the main scope, still got round stars.

[orly_andico]

This is the full APS-C frame:



I must say the $100 Orion non-reducing flattener is not a bad one.. there is a bit of star bloating close to the corners but the stars are still round.

[Gary]

Nice shot Orly! Love the hanging-in-the-sky framing.

[mymoon]

I was getting about 0.3 pixel RMS (about 1" RMS guiding) which is pretty bad.. but since my guide scope image scale is about the same as the main scope, still got round stars.

Great image. Using hyperstar you can reduced you imaging time to 13 mins.

when you and MooEy talk about XXsec/pixel I am lost. I don't see a need. Enlighten me if you will.

To me when I image say Eta Carina nebula I look at SkySafari Pro which gives the size as 120X120 arcmin.

I use this software for FOV values . Click here

I then for my imaging camera a 60D use the same Planetarium software and for the various lenses in my arsenal I found;

1. For a tight fit use a 400mm lense


2. For a good framing picture of just the nebula use a 135mm lense


and

3. for just the center star eta carinae itself use a C11


BTW the blue frame in the picture is looking at the Live View on the LCD.

I wish SkySafari would have a filter giving recommendation for the focal length of the telescope to use to image their "Tonight's Best"

more developed than this.

cheers

[orly_andico]

Agreed, Hyperstar (or a Tak Epsilon, or a Boren-Simon Powernewt) would reduce imaging times significantly.

However.. I know that Hyperstar is very sensitive to collimation. Ditto for the Powernewt.

The best solution is the Epsilon, because (so I've read) it holds collimation like nobody's business. Unfortunately they are crushingly expensive, even compared to Hyperstar.

The new Epsilon 130D is being sold by Peter Lee (tan14.com) for 3000 SGD flat. It's f/3.3 so the focal length is 429mm, about the same as a C8 with Hyperstar. It is a bit slower and would require 2.7X longer exposure times than a C8 Hyperstar. But still, I could take 5-minute subs to the same depth as my AT90EDT.

I can't imagine spending very much more than that. I know a Hyperstar + C11 is cheaper. But it's not premium the way Takahashi is premium.. and I don't want to deal with collimation. Of course the FSQ106 or Borg 125SD + Super Reducer are also at the f/3.6 range, but they cost even more.