Which DSLR?

[gonzostar]

As some of you may know my second hand canon 450d DSLR is caput after 18 months of good use!

I am now thinking should i go for another 450d

cheaper, sensor size 22.2 * 14.8, 230k pixcels

 or the 50d sensor size 22.3 * 14.9, 920k pixcels, which is about £100 more expensive

Or am i missing a trick? 

Or could  i get  a "astro camera" for  £300?

Thankyou

Dean 

[Dr_Ju_ju]

There are a couple on Cheap Astrophotography, see here http://cheapastrophotography.vpweb.co.uk/Available-Cameras.html

[Alien 13]

MPB Photographic have 650/700 D for less than £300 with low shutter counts.

Alan

[geordie85]

I'd go for a 600d that's been Astro modified simply for the low noise and swivel screen

[iapa]

I'm happy with my astromiser modded 600d (acquired 2nd hand from Buy and Sell)

Then again, I am also happy with the unmodded 700D 

The major advantage of either of these models over earlier is the articulated screen.

One day weather permitting I will do a side by side comparison of both as they have very similar (if not the same) sensor. Both have an expected shutter life of 100K.

Sensor (h)	Sensor (v)	# pixels (h)	# pixels (v)	pixel (h)	pixel (v)	pixel area
22.30	14.90	5184	3456	4.30	4.30	18.49

[iapa]

I should note that for a longer fl OTA, then you could be over sampling with either 600D/700D.

 

[gonzostar]

Thankyou all for your ideas  and feedback

Thanks Julian There is some interesting ideas on this site

For my budget people seem to be pointing me toward the 600/ 700d. Just a couple of questions i am note sure what is ment bu shutter counts? It would be interesting to have a comparison image, 

Also iapa i have a 8"SCT with the 6.3 focal reducer. What is oversampling?

My old 450d was unmodified, should i get new camera modified?

Cheers 

Dean

[Alien 13]

Shutter counts give an indication of the cameras usage anything up to 20K might be reasonable the usual life expectancy is somewhere around 100K. 

Alan

[iapa]

Shutter count is simple the number of times a picture had been taken with the camera.

It is recorded in the EXIF metadata saved in the image from he camera.

Over sampling...... short answer: too many pixels to a star

Slightly longer answer:

It's related to 'pixel scale' which is and measured in arc-seconds per pixel and calculated by:

pixel size/focal length * 206.3

When the light from a star reaches the camera sensor, it covers a number of pixels.

With larger pixel sizes, one star may only cover one pixel. With smaller pixel sizes it will cover many pixels. You need a camera which is a compromise between too few and too many pixels being covered by a star. Focal length, as noted above is also a factor.

With the longer fl, you get 'bloated' stars.... remember that in actuality a star is a point source light, not actually a circle.

Two images, NGC7635 (I did not pick the best of each set) one with an 80mm f67.3, 600mm fl refractor. the other with the 8" SCT, f10, 2032 mm fl without reducer fitted. Both with Canon 600D.

Notice in the later that the stars are much larger - 'bloated'.

HTH ?

 

[gonzostar]

Thankyou for the clear explanation and the images very useful. One more thing to think about which is part of the fun. I presume focal length in the equation is in mm? and oixcel size in microns

This explains why my images of star clusters and m45 where "bloated"

Is it worth gettibg  a "mod" camera?

 

Dean

[iapa]

13 hours ago, gonzostar said:

Thankyou for the clear explanation and the images very useful. One more thing to think about which is part of the fun. I presume focal length in the equation is in mm? and oixcel size in microns

This explains why my images of star clusters and m45 where "bloated"

Is it worth gettibg  a "mod" camera?

 

Dean

Correct millimetre and micrometer measurements.

I have a modded 600d and an unmodded 700D.

I'll take a look to see if I have anything from each of the same target and post here

Actually, earlier today Friday looked like clear from midday through to midday Sat. I could try something then with both of them, I can do with more data for any thing. Beside I've said a few time that I would do that anyway.

It probably would not be with the 6.3 reducer as I still do not have an extension tube to get the 55mm from the fr lens to sensor.

Edited January 10, 2017 by iapa

[gonzostar]

That  would be great. It will be interesting to see your results. Hope the weather holds out. Bit gloomy down south coast at moment!

[iapa]

On 11/01/2017 at 13:51, gonzostar said:

That  would be great. It will be interesting to see your results. Hope the weather holds out. Bit gloomy down south coast at moment!

I've not forgotten that I was going to do this.

The weekend in question turned out to be a wash out really.

Last night looked as if it had potential, but I took a while to get setup and guiding - haze was preventing me plate solving

Just got to keep trying

[gonzostar]

Thanks for your efforts. One thing this hobby teaches us is patience!  

[dannybgoode]

I picked up a Canon 500D in absolutely mint condition for £129. Gives me plenty of change to get it modded and will be fine to get me going. 

Look at the used section of the following camera stores. I have used them all at one point or another and ask are excellent:

Harrison Cameras 

Clifton Cameras

Park Cameras

Wex

All have an excellent range of decent second hand bodies. 

[gonzostar]

Yep still waiting for mine to be fixed, but all the above look useful to. Better to have a spare rather then borrowing someone elses!

[iapa]

Finally.......

I have some images from both 600D (modded) and 700D.

each is 5 x 600s ISO400 of Bode's nebulae . centred on SAO 15014

50 BIAS images specific to each camera

Nebulosity used for post processing:

• created a master BAIS (stacked, no alignment, average/default)
• Preprocessed - used the master BIAS as DARK
• 43 FLATS (specific to each camera)

Saved as JPG to upload.

1. 700D stacked and cropped, saved as JPEG

2. 700D, corrected background and colour balance stretched a little

3. modded 600D stacked and cropped, saved as JPEG

4. modded 600D, corrected background and colour balance stretched a little

 

 

[gonzostar]

Thankyou so much for all your efforts. Very much appreciated

I think i will need both camera that is unmodded and another modded  Although the modded seems to bring out more detail 

I also have in my armory now a  Scientific explorer 102 APO refractor. Looking at Astronomy tools these cameras are ideal.

Hopefully i am upto the job to!

Cheers and clear skies

Dean 

[iapa]

The images need a lot more work.

Here's a link to the raw and calibration frames: https://drive.google.com/drive/folders/0B9CQtccAk72ZbDZDcDhNZ0VUMW8?usp=sharing

 

[gonzostar]

Just thought will a CLS light pollution filter enhance or "spoil" images with a modded camera?

[iapa]

I had a 2" light filter fitted at the time - it's packed ready for my holidays, but gimme an hours or so to try to dig it out.

[gonzostar]

Going anywhere nice? Iam visiting  "home" Yorkshire next week. Taking the binoculars to the peak district. Hopefully dark clear skies!

[iapa]

Orkney Islands, 

with CGEM-DX, AVX mounts, the DSLRs, ED80, ST80, 200P-DS and possibly the 8" SCT with cables, power and a couple of PCs and a laptop.

May find room for a change of clothes - which is OK as it's fully furnished and the washing can go on during the day while I sleep

 

 

Edited April 4, 2017 by iapa

[gonzostar]

That sounds awsome!

[Adam J]

The 550D, 600D, 650D and 700D all have exactly the same sensor in so far as I am aware. Its possible that they may have different image processors.

The 550D is a little more compact so tends to have slightly more noise as it gets warmer. As for the others, it wont make much difference beyond the normal variation in quality from sensor to sensor.

Overall it will be a challenge to tell them apart in terms of astro-imaging performance.

I would not get the 100D because it is also compact and suffers from thermal noise, the 500D is just a noisy sensor compared to the 450D and the 1000D is actually shockingly good due to its larger pixels and efficient sensor making up for the apparent disadvantage of higher read noise.

So ultimetly get another 450D or a 600D or if you want to try Nikon the D5100 is actually very good once you switch to the aftermarket firmware.

If you have money burning a hole in your pocket the 6D is very nice.