The noise produced by a Canon 1100D at various ISO settings and temperatures

[Gina]

Yep! Got it second hand - Atik 314L+ Gold Edition Now I want an Atik EFW2 filter wheel to go with it. Plus some filters, of course, though I've already got an Astrodon Ha.

[Chris]

Well done thats brilliant:) I'll be interested to see how you find CCD imaging after using DSLR's, I know they are two completely different animals.

[jnc71106]

I suspect Gina is going to be pleasantly surprised

[Ags]

Those poor 1100Ds are going to get neglected...

[Gina]

Those poor 1100Ds are going to get neglected...

Not entirely Agnes. They provide a large OSC sensor which I will still want for larger objects. Also, having several imaging systems available as the same time makes for better use of available clear skies. I shall also still be using one as a long exposure finder.

I do plan to try out the 314L+ with camera lenses though for wide field NB, particularly the 200mm SMC Takumar but I need to sort out an M42 x 1mm thread to T2 adapter.

[JamesF]

What will actually happen is that Gina will decide she needs a second pier, mount and obsy for the additional imaging rig

James

[Gina]

I suspect Gina is going to be pleasantly surprised

I like the Artemis Capture software Been playing with the scope pointed at the far hill with the A30 to get focus somewhere near so that I can be in "the right ball park" when I point it at the stars or Jupiter. The display zoom feature is very nice for fine focussing. The resolution is much the same as with my 1100D which it should be because the pixel size is much the same. The focus is very critical when zoomed in to show the pixels. The atmospheric effects are clear too with the image moving about a bit (by a pixel or so) and the focus coming and going). The range is about a mile.

[jnc71106]

Hopefully you will be able to point the camera at something a bit more interesting than a hill soon Gina

[Gina]

Hopefully you will be able to point the camera at something a bit more interesting than a hill soon Gina

Well I took some nice pictures of trees, a house, an estate agent's "To Let" sign and a road sign but it saved them as FIT files and I don't seem to have anything with which to view them. PS says it can't read them.

[jnc71106]

FITS liberator plugin for PS should sort that out

http://www.spacetele...fits_liberator/

however your stacking program will probably give the option to save it as a TIFF file once stacked

[Gina]

Got AC saving as TIFF and here's a nighttime image processed in PS

[jnc71106]

not bad but i think you have blown the core a little

[Gina]

FITS liberator plugin for PS should sort that out

http://www.spacetele...fits_liberator/

however your stacking program will probably give the option to save it as a TIFF file once stacked

Thank you - I'll check it out

Yes, DSS saves as TIFF

[Gina]

not bad but i think you have blown the core a little

Yeah, just a little Clear skies forecast for tonight so I'm hoping to point it at something rather more interesting I have an Ha filter ready in a manual filter wheel.

[Ags]

I've got the USB drive with all 3,600 Gina-files - I will start processing them on the weekend :-)

There is not enough room on my hard drive, it's lucky I bought an external drive a few months back.

[Gina]

I've got the USB drive with all 3,600 Gina-files - I will start processing them on the weekend :-)

There is not enough room on my hard drive, it's lucky I bought an external drive a few months back.

Glad you've got it alright Yes, there's quite a lot of data to analyse there Looking forward to the results

[Gina]

I now have the cooling in the 1100D box working properly again. I think the camera might have moved and lost full thermal contact between cold finger and Peltier TEC. Made sure the cold firnger was in good contact and at the same time rejuvenated the silica gel bags. Put it all back together and used insulation tape to make a good seal around the bayonet.

Just had it set up in my observatory and been testing it. Good results The humidity is really low having "cooked" the silical gel bags and filled the space round the camera with them. 7% R.H. when first connected. Rose a bit when the cooling was on but still maintained a dew point of -15C. With the cooling on MAX the cold finger temperature reached -14C with an ambient temperature of 14C so that's a maximum cooling factor of 28C below ambient. Heat sink was running at 5C above ambient with the fan on full. R.H. was 15% at MAX cooling.

Have to say, I'm very pleased with these results

[Ags]

I have all the files converted to tiff... There were six unreadable files out of nearly 2000 RAWs.

[Gina]

I have all the files converted to tiff... There were six unreadable files out of nearly 2000 RAWs.

Well done Agnes Sounds an enormous job!

[Ags]

Running the images through my analysis program was an even larger job. It took 25 hours of processing (I had to restart once). And now I have the manual analysis to do :-)

It will be a while before I get through all the data, but I did a quick camparison between median stacked darks at different termeperatures, and the average of the results from unprocessed darks.

If you recall I initially announced that noise was fairly constant across temperature ranges and cooling was largely irrelevant. That was from looking at darks without applying even rudimentary noise reduction by median stacking. This is the result for ISO 100 and 60 second exposures at a range of temperatures:

If I add in a simple median stack to remove the random noise (remember however I have only 3-4 images per temperature-exposure-iso point to use in a median stack) we see a totally different picture, with random noise almost completely eliminated, and non-random noise showing a smooth increase across the temperature range:

I'll start a new thread for the results - I think it would be a shame to Bury Gina's work at the end of a long thread.

[Ags]

And here are some more showing the difference between raw noise (flat) and nonrandom noise (temperature-dependent).

It occurs to me though that unless tracking is pefect, even nonrandom noise will be reduced by a median stack.

[Gina]

Initial results look very interesting Agnes I agree about presenting the full results in a new thread - thank you for thinking of that

I plan to set up for the missing data tomorrow. I'll send you the data files via Dropbox after deleting the bulk data files from Dropbox to make room.

[Astro_king]

I ended up buying 450D instead of 1100D because I wasn't sure how to modify 1100D myself.. I still don't know if it was a bad decision though.. good comparison though

[Gina]

I'm not sure about the 450D all I recall from when I did my research is that the 1100D came out as being just about the best for astro imaging - as good for noise figure as any other model but cheaper than the others that had similar noise levels. That was why I choose it. It also has pixels of a similar size to many astro CCD cameras. There are others with higher resolution and smaller pixels but smaller pixels will be less sensitive. The resolution of the 1100D seemed about right for astro imaging. I'm not saying other models would not be perfectly acceptable for modifying for astro use just that if you're looking for a DSLR to buy for dedicated astro use then the 1100D represents the best value and you won't get any benefit for paying more. Older models may be cheaper but many lack the properties either essential or beneficial for astro use.

[Gina]

Further data acquisition for this project will rely on my getting the 1100D cooling system working correctly. At present I have a problem with thermal conductivity from sensor to the cold side of the TEC. The main problem is thermal contact between cold finger and image sensor. I'm getting around a 9C temperature difference between EXIF T and cold finger temperature whereas when it was working right I got very little difference. The reason for thermal loss seems to be inadequate rigidity between cooler and camera. This has meant I'm going for a version 3 of the cooling system mechanics. The details will be posted in the new thread http://stargazerslounge.com/topic/171415-1100d-set-point-cooling-with-peltier-tec-and-air-cooling-v3/ in the DIY Astronomy forum.