Peltier cooling of 1100D sensor chip

[Gina]

Mindburner,

if you only remove the colour balance filter, the remaining front filter, the anti-alias/ dust filter provides the UV-IR cut-off. No need for an additonal filter unless you need AF etc.

Yes, unless you want to do near infra-red imaging (and there doesn't seem all that much scope for that compared with all the rest) I think it best to put the front filter back. Pity you need to take it out to get to the back one. You just need to make sure you have a very clean, dust free, place when you open up the sensor. Apparently, the Canon filter is at least as good as a Baader or any other filter. You need to be very careful getting it out so as not to break it or even stress it too much - just work round the edge of it very carefully with a craft knife after cutting the glue. I went round mine several times gradually easing it up until I finally broke the last bit of glue between the filter and the frame.

[mindburner]

Mindburner,

if you only remove the colour balance filter, the remaining front filter, the anti-alias/ dust filter provides the UV-IR cut-off. No need for an additonal filter unless you need AF etc.

ah so if I remove the blue filter, I dont actually need the baader filter? I was going to use this for LP reduction. Would having technically two filters on the camera (the original and the baader) cause any issues do you think, maybe cut too much light.

Is it worth removing both filters and ise the baader only?

[Merlin66]

No.

There's nothing added by using the Baader.

[Gina]

To clarify (if wanted) - carefully remove the front filter which is clear and put it carefully to one side wrapped in lens tissue (as per Gary Honis's instructions). Then remove the blue (colour correction) filter and discard it (it blocks deep red). Then take the front filter from the wrapping and carefully glue it back in. Being careful not to breathe on the sensor or get dust on it.

Front filter removed - this is the keeper. Leaving the other (blue coloured) filter to be removed :-

[Merlin66]

I only removed both filters to get the wider 380nm to IR response for spectroscopy.

[Gina]

Yes, I remember you saying that.

Here's the blue filter removed (and broken but I didn't take as much care with this one as it wasn't wanted) leaving none in the frame.

[Gina]

I still have my Canon IR/UV blocking filter from the 1100D and considering putting it back. I have a CLS-CCD clip in filter which provides both IR/UV and LP blocking so that should stop dust ingress as well as filtering. But this changes star (and planet) colours so I was thinking of taking this out for some images to get full colour. Then replacing the Canon UV/IR filter will block IR and protect the sensor. Putting the CLS-CCD filter back in would just block LP.

[iwatkins]

Top tip, if you are doing filter changes, sensor cleaning etc. and you don't have a clean room (and who does), use the bathroom.

Get your kit setup, shut the door, wear talc less latex gloves and run the shower for a bit. This will pull a lot of dust out of the air while you do what you need to do.

Cheers

Ian

[Gina]

Top tip, if you are doing filter changes, sensor cleaning etc. and you don't have a clean room (and who does), use the bathroom.

Get your kit setup, shut the door, wear talc less latex gloves and run the shower for a bit. This will pull a lot of dust out of the air while you do what you need to do.

Cheers

Ian

Yes, that's very good advice

[Auntystatic]

I have a CLS-CCD clip in filter which provides both IR/UV and LP blocking so that should stop dust ingress as well as filtering. But this changes star (and planet) colours so I was thinking of taking this out for some images to get full colour.

Interesting that your getting colour changes as the Astronomik web site says "colour balance is near perfect " for attaching to a modded dslr. I've just ordered one hoping it will arrive on Tuesday in time for some of this weeks clear skies.

[Gina]

In view of the fact that the wavelengths of sodium and mercury vapour lamps and nearby are blocked, there is bound to be some change in colour balance as I see it.

I'll take some terrestrial views with and without CLS-CCD filter using my currently unmodified 1100D camera and post the results. I'm in no great hurry to swap sensor assemblies yet. I've got a number of things to sort out before an IR modified camera will be of much benefit over unmodified.

[Gina]

The CLS-CCD clip filter definitely gives a blue bias in colour. Two photos of more or less the same view with and without CLS-CCD clip filter. Taken a minute or two apart (time taken to remove filter). Both photos are at the same exposure.

[Gina]

And now two solar images from this afternoon - with and without CLS-CCD filter.

[Gina]

SO... I'm going to put my Canon IR/UV filter back in the filter frame and only use the clip in CLS-CCD filter for low altitude objects suffering from LP. Had I known this a while back I could have saved some money Oh well, we live and learn!

Anyone suggest the best glue to use to glue the filter in?

[Auntystatic]

Hmmm very interesting, when I did my mod my images turned pink, the ccd-cls is supposed to return a near natural colour so not sure why you got those results. Unless you have a custom white balance set and saved it with the images as jpg. I guess I'll find out when mine arrives if I've made an expensive mistake.

Thanks for the tests Gina.

[Gina]

Those photos were using an UNmodified camera. As I understand it the CLS-CCD filter is supposed to give a 99%+ transmission over most of the visible spectrum with a very sharp cutoff at IR and UV plus block bands for the primary light pollutants of Sodium and Mercury. The CLS is similar but without the sharp IR cutoff. The CLS basically acts as a very good LP filter and the CCD version includes sharp cutoff IR and UV to cater for no IR/UV cut filter in the camera. It is not to correct the colour balance - i.e. it retains the improved deep red response of the modified camera.

Anyway, that's what I thought.

[Auntystatic]

This is the bit from their website, it does actually mention a colour shift in unmodded cameras, I missed that bit ooops..........

• DSLR photography (original): Very good, colour balance shifted but contrast enhanced
  
• DSLR photography (astro modified): Very good, colour balance is near perfect
  
• DSLR photography (MC modified): Very good, colour balance is near perfect
  
• Webcam / Video (Planets): Unsuitable
  
• Webcam / Video (Deep Sky): Very good, if light pollution is a big problem
  

Technical Data

• 95% transmission at 486nm (H-beta)
  
• 95% transmission at 496nm (OIII)
  
• 95% transmission at 501nm (OIII)
  
• 97% transmission at 656nm (H-alpha)
  
• pass from 450 to 520nm and from 640 to 690nm
  

I'll have to use this now untill I can get funds for the MC clear glass filter to replace my busted canon 1st filter, I like the idea of having dust prevention in front of the sensor.

[mindburner]

hi Gina

I have just got my 1100D kit and it's a pretty nice camera. There seems lots of good software and support in the astro community (and super posts like yours), plus I don't fancy modding my Nikon.

It's sitting on the desk in front of me surrounded by tools.

I almost hate the idea of pulling it apart. Almost:)

If I can just ask a quick question.

I was going to keep the 1st filter in place and only remove the blue colour filter to get more red response for DSO astro work.

then....

I saw some nice IR shots of snow/trees etc and though I may remove both and use a front lens mounted filter just to let IR in and I already have a Baader filter for astro work. I think I will need one or more astronomik clear glass 'filters' to keep the autofocus happy though which will add cost, plus as I think you mentioned, the Canon IR/UV filter is pretty good and worth keeping in.

what would be your opinion?

[Gina]

Sorry for late reply - I though I had answered this one.

If you would like NIR response for infra-red imaging then you will want both filters removed. As you say you can use an external IR blocking filter for visual light use. This could be either a screw on one or a clip filter. I have an Astronomik CLS-CCD clip filter. This blocks IR and UV and also light pollution from the usual street lights (sodium and mercury vapour). Not cheap though.

If OTOH you absolutely don't want to take IR photos or IR AP then the Canon front filter is as good as any at blocking IR and UV.

I hope that answers your question.

[Gina]

Regarding cooling and noise levels, I'm currently running a series of dark subs with ISO 3200 with exposures of 30, 20, 15, 10, 5, 4, 3, 2, 1 minutes, 2 of each. Sensor temperature was 13C for the first 30m exposure and the noise was just visible. Later the sensor temp had risen to 18C and the 20m exposure seemed to give much the same noise level. I've read somewhere that noise doubles with each 7C rise in sensor temperature - this result seems to support that. This shows the benefit of cooling the sensor.

[Gina]

Peltier TEC PWM power control circuit.

[Islander]

That's not a million miles from the circuit I use as a dew heater controller - cheap and very effective

[Gina]

Of course, this is just manual control - no automatic temperature control. This should cool to a certain temperature difference between ambient and sensor rather than "set point". I'll probably see how well this works before thinking about automatic "set point" control.

[Gina]

DONE IT! Swapped sensor assemblies and camera works fine

And now I've found that there is a way of getting cooling copper out though the camera side. Or should that be in? When I'd got the sensor assembly in complete with the copper cold finger and before I put the back on, I could see a suitable gap next to the USB and other connectors. I could thermally connect the cold finger to the outside by attaching a strip of copper to the cold finger and taking it out through the side.

[mindburner]

yes it does many thanks. I have now modded the 1100D and I am just making a DC PSU for it so as I don't need to swap batteries every hour or so. I am very interested in the cooling mods as I want this camera to be better in the noise department than the Nikon I was using and cooling seems to be the way to go. I am using backyard EOS but have not had a chance to use the camera in anger so to speak as yet