Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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This may seem like a pretty basic question, but I'm trying to figure out a good starting point for some basic widefield imaging.
I've been shooting some tripod mounted shots this week with my new DSLR. I've basically just set the timer for 30 second exposures, ISO 800, shooting at f/4.0 at 18mm or f/5.6 at 55mm. But tonite I am going to put the camera piggyback on my scope and track it because I'm not happy with the amount of trailing I am getting in my images, and I would like to increase the stellar density.
I would think the LXD75 would be pretty forgiving with tracking at 55mm focal length with reasonable polar alignment, and I live in a fairly dark location so what do you think I can safely push my exposure times to for shooting in these ranges of ISO and focal ratio?
James
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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Here is an example of what I am getting right now.
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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fishonkevin
member
Reged: 04/29/07
Posts: 72
Loc: Michigan
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I routinely get 3 mins on my LXD-55 with a rough polar alignment. You should at least be able to get the same, depending on your LP. I shot the Summer Triangle at my dark site using that set-up. Here is a link.
http://farm4.static.flickr.com/3335/3668505803_88f902034f_b.jpg
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Kevin
W.O. ZS 105
Meade AR-5
GM-8
LXD-55
Rebel XT Modified
Quantaray 300mm Mirror Lens, Ziess 135mm, Sigma 24-60mm APO
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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I would start at ISO 1600 rather then ISO 800. Another forum member (hello Samir!) recently gave me good advice on how to figure out the minimum exposure times for any given site to ensure the actual image data is separated from the read noise from the camera. His web page with that advice is here. Basically you want to look at the histogram and make sure the large peak caused by the skyfog is separated from the start of the graph.
From looking at the noise in the that sample image I *suspect* a longer exposure is what you want. For my skys at f/4 I seem to need a 60-second exposure @iso1600.
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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Even though I should use ISO 1600, I'm going to stick with ISO 800 for tonite and bracket shoot 60, 120, and 180 seconds so I have a means of comparison since I am shooting from a different site than last evening (home this time), that will give me an honest comparison, but I am going to track it and see how it improves the outcome. I think I am safe to shoot 120 seconds but I'll look at the back of camera histogram to make sure, and make adjustments as needed. I'll know in about 8 hours what my sky fog limit is. The site I was at last evening is amazing to say the least.
Since I am fairly new to all of this, I've had to learn a lot of things for the first time, but in all honesty it's not too bad at all. Converting files, dealing with DSS, and making level adjustments has been pretty easy to grasp, and I do think reading this forum for the past couple of months has helped me a lot in understanding the basics enough to get going with it. I was actually shocked that I got the results I did with only a fixed tripod knowing so little, I just know that I can improve on that a whole lot with tracking.
Wish me luck.
James
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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s58y
Postmaster
Reged: 12/12/04
Posts: 5509
Loc: Eastern NY
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I shoot from a suburban/rural transition site with moderate light pollution (average darkness with no moon is perhaps 21.4 with the SQM-L). 5 minutes at ISO800 with no filter at f/4 is quite reasonable. With something like the IDAS LPS or Astronomik CLS, 10 minutes at f/4 is possible at ISO800.
Isn't there a bright moon out tonight, though? This will overwhelm any moderate light pollution. Maybe you can sneak something in before moonrise.
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Hutech 30D, SBIG ST-402 autoguider
SV80S, TV102iis
Old camera lenses: 800mm f/5.6, 180mm f/3.4
AP900, Barndoor tracker
http://www.pbase.com/s58y
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Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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How does this look? This was 10 times 120 seconds at 55mm f/5.6 - M31 - cropped and reduced - which makes the star images slightly larger. This was done piggybacked on the SN6 with no guiding.
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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Not bad - you have some dust-lane detail in there!  I know that is a fairly small target at 55mm so it is hard to get details out of it. Looks like your tracking was reasonably good.
Is it possible to post your raw data (those 10 frames)? I am curious to see what the source material was like, and perhaps can give processing them a try myself...
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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Here's another one. All exposure information is the same as the previous one. I shot a bunch tonight just trying to get a feel for it. This is the Double Cluster in Perseus.
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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Falcon-
sage
Reged: 09/11/09
Posts: 242
Loc: Gambier Island, BC, Canada
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The double cluster is nice and sharp - looks good.
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Tasco 11TE-5 'Lunagrosso': 4.5" Newtonian, 900mm f/7.9
Meade DS-2114S: 4.5" Newtonian, 1000mm f/8.8
Galileoscope: 50mm Achromatic Refractor, 500mm f/10
Tasco EQ-2-like mount w/ clock drive
Celestron CG-5GT mount
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Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3453
Loc: Santa Cruz Mountains , CA
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Your off to a great start , well done.
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Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
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Jimmy2K63
Pooh-Bah
Reged: 04/26/09
Posts: 1193
Loc: Kentucky
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Thanks Erik. This just blows me away. This was taken with the Pleiades very low in the sky, with some light pollution just below it. I can't believe I am catching some nebulosity with only 20 mins of exposure time.
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http://astronomyguy63.blogspot.com/
LXD75 SN6-UHTC
Cave Astrola 10" f/5
Garrett 15x70/FarSight
Canon XS (1000D)
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Nils_Lars
Post Laureate
Reged: 01/04/08
Posts: 3453
Loc: Santa Cruz Mountains , CA
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Oh ya your hooked , hehe.
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Erik
Orion Atlas Self Hypertuned (EQMOD)
Orion ED 80
Williams Optics VII reducer
Celestron 8" SCT
Orion Starshoot Autoguider
PHD guide
Canon 400D Hap Griffin Mod w/Baader filter
Astronomik clip-in LP filter and 12nm Ha
Stilleto CVF and Bahtinov mask
Tamron 75-300mm&28-80mm lenses
NexImage webcam
http://www.flickr.com/photos/31986095@N05/
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