Modded DSLR question

[A Rnam]

Has any of you used a Canon 450D (or older) camera with just an LPF2 delete? 

I am currently doing only Visual and casual photography with lenses and an iOptron skytracker. I know someone who is selling a camera with the IR filter (LPF2) removed. The question is, will I need an additional UV/IR filter to image with my lenses, or can I get away with the filtering that remains on the front (LPF1) filter? I would like the flexibility of being able to image without additional filters (especially since I can't expose for long on the Skytracker).

Thanks!

[Glenn Newell]

Well I can tell you that I have two full spectrum Canons, A T3i and recently a T3. 

I typically image through a Astronmik CLS filter (light pollution) and had switched to a Astronmik CLS for CCD filter because I do have some glass in my optical train (focal reducer) but honestly I cannot say I have seen any difference between the straight CLS (no IR/UV filter) and the CLS CCD (with IR/UV filter).

I guess you are using camera lenses?

In any case I can really recommend the astromodified cameras as I have compared shots of M42/43 with stock canon t3i to full spectrum t3i and t3 and there is a huge difference in color and detail. Depending on exactly how the mode was done will determine what you can do with the camera outside of AP. Both of mine will autofocus and take terrestrial daytime photos. They just need white balance adjustment. The T3i, which has sensor cleaning, doesn't do sensor cleaning with the mod.

So if you want to use the modded camera for terrestrial as well, be sure to ask if the auto-focus still works, and ask how many shutter activations it has.

http://www.dpreview.com/forums/post/29343271

 

http://www.shutteractuations.com/canon-eos-camera-shutter-lifetime/

Glenn

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[Aravind Ratnam]

Thanks Glenn, that is very useful.

Yes, I will be using a wide assortment of camera lenses (from 12mm to 400mm although the latter is a bit much for the Skytracker to handle). 

By "full spectrum", I presume you have removed both filters (lpf1 and lpf2- the latter is the "bad for ap" filter) on each camera. Have you also cooled/debayered your cameras?

Apparently the 'star bloat' issue becomes only apparent with very careful histogram stretching. The reason I don't want a cls filter in my optical train is because I can't expose for long with my current setup - I have just started to use a didymium filter (a poor man's cls) instead that does not necessitate much longer exposures but still fights pollution.

 

Question/request:

Do you (Glenn) or anyone on the forum have a similar Astro modded camera (with either lpf2 removed or substituted by a baader/astrodon) to sell? 

Aravind

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[Glenn Newell]

Aravind,

I am traveling right now so don't have access to the paper work on my cameras but both are full spectrum. The IR filter removed and glass of the same thickness substituted so that autofocus still works. My T3i I bought 2nd hand from someone on cloudynights who had it modded by Gary Honis (Hypercam). I paid around $700 in a year and half ago. My T3 got a similar mod done by the owner, who had done multiple canons before, and I paid $225 (!) a month ago.

The t3 will be used for wide field on camera lenses and/or on my portable rig with a 500mm mirror lens or my 6" RC.

Yes I cooled my t3i and it lives on my home more permanent setup with an 8" RC. The cooling mod is a cold finger and ice water circulation.

I can point you too some photos and stuff if you want to know more about the cooling project. 

I have not Debayered either camera, and won't. At that point I would probably switch to CCD, but as I have access to pro CCD, scopes, and mountain top sites via iTelescope.net it's hard to justify owning a CCD for me at this time. 

It is possible that the club will own a CCD at some point in the future, maybe the new qhy miniCAM5F+9 filter. Too small a chip I think but a good platform to expose people to CCD and narrowband as the price is right (precisely because the small chip size allows for less expensive smaller filters) and mosaics to get a larger FOV can always be done.

Anyway I recommend you shop on cloudynights classified and ebay for used astro modded camera, Or get a used body and have it modded.

I personally don't see the need for anything newer that a t3i, so you can save a lot of money there. The thinking is that newer cameras have higher ISOs (which don't help with AP except for faster previews, and 5 or 10 seconds at 12800 on a t3i is fast enough) and more pixels, which you probably don't need because you will be "oversampling". That is to say you won't get anymore detail with more pixels because you will be limited by the typical 2 arcsec of "seeing", unless you are at a mountain top observatory site.

But others may argue. One possible exception is the new Nikon AP DSLR. Its very pricey but they've done something to make the read noise so low that you may not need cooling or darks (If we can believe the reviews).

Cheers,

Glenn

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[ja...@znet.com]

If you have no UV/IR filter or a full spectrum you will see blooming on long exposures with refractive optics but not reflective optic without narrow band filters. If you are doing narrow band you are essentially working monochrome as far as focus is concerned.

Mirror optics reflect all frequencies of light the same so they all focus at the same point. A Newtonian or Classical Cassegrain are two examples.

A refractive optic is a single or multiple prismatic element which bends pr refracts light to a focal point, By using multiple elements positive and negative plud different types of glass we can get more frequencies to focus at a given point, This is fine for normal daylight exposures which are short and are only in the normal visual range. This is what camera lenses are designed to do.

The problem arises when you add theUV light and the IR light which is normally filtered out. The lenses are not designed to cope with these frequencies so they don't focus at the same place as the regular frequencies. Rather nearer or farther. Some older lenses have an infrared index mark to indicate the difference in focus on old film cameras and lenses of that age and type. Bloom can be ab issue in just about all refractive systems if no filters are used. This includes triplet APOs and even my Quad APO and my 9 element ED 300mm f/2.8.

Summary if you shoot single frequency (narrow band) you want full spectrum. If you do one shot color you need a filter. There are several filters on the market that will pass farther into the red without adding in the UV end if you want to modify your camera. This is not a project for everyone, you can destroy your camera. Better to buy a filter and have a tech do it. How do I know? I destroyed a Nikon D70 that way.

To start keep it simple and use a regular unmodified camera. After you get to a point where it limits you go the astro mod with a U/.IR filter. For narrow band you really want an appropriate mount $$$$$$$$ then an application specific camera $$$$ and good filters $$$$ and finally specialized optics $$$$$$.

Learn to use what you have before spending extra money, Learn from others. Have fun.

Jack

Current cameras do ok if you stack lots of shout exposures. You may be surprised.30 60 second exposures at ISO 3200 with a Nikon D800 and the 300mm show the rosette pink but not at all bad.

Simple setup, simple mount (IEQ45), no guiding required.