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  #21  
Old 18-10-2010, 09:28 AM
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Octane (Humayun)
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Martin,

If imaging with a CCD, to stop the lens down, attach to EOS camera, select desired aperture, press the Depth-of-Field Preview button, and remove the lens from the camera whilst the button is pressed.

Furthermore, if imaging with a DSLR, if you use the EOS Utility's Remote Live View feature, you are able to nudge the focus on the lens through the software; you need to put the lens in AF mode first. Once focus is achieved, flick back to MF, disconnect and shutdown EOS Utility, connect to Maxim DL, and you should be good to go.

Hope this helps.

H

Last edited by Octane; 18-10-2010 at 10:12 AM.
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  #22  
Old 19-10-2010, 09:12 AM
Martin Pugh
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Thanks again.

Gary - I think its Marco that uses a Pentax EDIF lens, which are hard to get I understand but absolute pristine for astrophotography. I also understand its impossible to get a Pentax lens to CCD camera adapter, but Pentax Lens to Canon adapters are readily available.

Humi - thanks for that tip - I hadnt realised you could alter focus from within the EOS utility. (I am very new to DSLRs!). That's a great tip - saves running out to the scope at every focus frame.

Doug - So, let me understand clearly. The 70-200 f4L IS USM lens is a much better performer than its f2.8L equivalent?
Questions: Why did you opt for the more expensive IS version - is IS really necessary when the lens is used for astrophotography?

Do DSLR astrophotographers use any sort of filter on the front of the lens, like a UV cut? Clearly, the more expensive ED lens might not need it but perhaps the cheaper ones do.

cheers
Martin
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  #23  
Old 19-10-2010, 11:26 AM
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Quote:
Originally Posted by Martin Pugh View Post
Doug - So, let me understand clearly. The 70-200 f4L IS USM lens is a much better performer than its f2.8L equivalent?
Questions: Why did you opt for the more expensive IS version - is IS really necessary when the lens is used for astrophotography?
The range in order of performance/sharpness (as reviewed by daytime photographers)...
1. 70-200mm f2.8L IS
2. 70-200mm f4L IS
3. 70-200mm f4L
4. 70-200mm f2.8L

I went for the f4L IS as I wanted a very good daytime lens too where the IS will be handy.
The 2.8L IS was out of my price range and all reviews of the f4L IS found it be very sharp from edge to centre. MTF performance (pic below) at 135mm and 200mm is almost comparable with the equivalent primes
Kind of counter-intuitive in a way due to the extra lens elements used for the IS - one would think it would be less sharp than it's non IS sibling, but it's consistently reviewed as one of the sharpest zooms out there.

As you've stated, the IS circuitry is useless for astro work and should be turned off.
Doug
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  #24  
Old 19-10-2010, 12:07 PM
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Hi Martin,

Yep, EOS Utility Remote Shooting/Live View is indispensible.

The way I've focused in the past is to monitor the chromatic aberration on the star in Live View. With each nudge you give the lens, you'll see colour change from red to blue. Once you're in the middle, you know that you're pretty much in focus. It only takes a couple of minutes to do it. Of course, you could us a Bahtinov Mask and the Bahtinov Grabber software to take all the guesswork out of it. I don't have a mask small enough for a lens, but, I know Chris (Omaroo) does and his works beautifully.

And, yep, just disable IS whilst shooting; if you're running on batteries, you'll drain them pretty quickly with IS enabled!

H
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  #25  
Old 19-10-2010, 12:47 PM
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Quote:
Originally Posted by Martin Pugh View Post

Do DSLR astrophotographers use any sort of filter on the front of the lens, like a UV cut? Clearly, the more expensive ED lens might not need it but perhaps the cheaper ones do.
I use a Hutech IDAS LPS2 light pollution filter in front of the lens - a must have piece of kit!
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  #26  
Old 20-10-2010, 07:07 AM
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philiphart (Phil Hart)
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You'll generally need UV/IR cut somewhere in the optical train otherwise you'll get bloated stars with just about any lens I think. But you probably have that already with your rear filter (but less 'cut' than the unmodded camera) unless you opted for the 'clear' filter option.

I still use a UV/IR filter on front but that's mainly to keep dew, dust and anything else off the front lens element. I don't mind wiping a filter clean but I prefer not to touch the lens itself as much as possible.
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  #27  
Old 20-10-2010, 07:10 AM
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iceman (Mike)
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Quote:
Originally Posted by philiphart View Post
I still use a UV/IR filter on front but that's mainly to keep dew, dust and anything else off the front lens element. I don't mind wiping a filter clean but I prefer not to touch the lens itself as much as possible.
Unless you have a bright moon in the scene - then you're likely to get internal reflections and a second ghost blue/green moon image.

Then you'll need to remove the front filter.

But I know it's unlikely Martin will be photographing the moon
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  #28  
Old 20-10-2010, 07:14 AM
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Quote:
Originally Posted by philiphart View Post
You'll generally need UV/IR cut somewhere in the optical train otherwise you'll get bloated stars with just about any lens I think. But you probably have that already with your rear filter (but less 'cut' than the unmodded camera) unless you opted for the 'clear' filter option.

I still use a UV/IR filter on front but that's mainly to keep dew, dust and anything else off the front lens element. I don't mind wiping a filter clean but I prefer not to touch the lens itself as much as possible.
You must be lucky as i always get a reflection of a bright star etc in the image when i use a filter - i now remove them but use a dew strap and a microfibre lens cloth if needed.
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  #29  
Old 20-10-2010, 01:20 PM
Martin Pugh
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Thanks for all the input.

I took up the suggestion of renting, and searched the local area for a supplier. I have a shop in town who will rent me the 70-200mm f4L or the 70-200mm f2.8L lens for $45 a week. Its a pity they do not have any the primes.

But this is an excellent way to check out these lenses before I spend any more money. I will probably try and sell the 85mm once I have tried these out.

I will probably pick up a filter, used, and give that a try also.

cheers
Martin
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  #30  
Old 20-10-2010, 01:48 PM
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Good luck Martin - look forward to viewing your results.
Doug
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  #31  
Old 23-10-2010, 03:25 PM
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Gary - I think its Marco that uses a Pentax EDIF lens, which are hard to get I understand but absolute pristine for astrophotography. I also understand its impossible to get a Pentax lens to CCD camera adapter, but Pentax Lens to Canon adapters are readily available.


Hi Martin,

Ashley at Precise Parts can make one of these. I have already talked to him.

He wants one of those Canon to Pentax adapters and he will machine it or attach it to another adapter that fits the FLI Filterwheel.

I have purchased several Pentax lenses for use with my Proline 16803.
I have the non-ED 300mm F4 67 lens, 105mm and 165mm.

The Pentax 67 300mm EDIF F4 is rare and I haven't even been able to find one for sale. The 400mm F4 ED - there was one available on Ebay but it was expensive - about US$2800 or more.

Greg.
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  #32  
Old 26-10-2010, 06:39 PM
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Canon EF 200mm f/2.8 L II Prime focus lens

So more options are given I'll pipe in and say I am having a ton of fun and very happy with the Canon 200mm L series prime focus lens that I had already very much enjoyed for years for daytime shots. It yields 5.3 degree wide shots in front of a Qsi583 camera with filter wheel so this lens can do narrowband or LRGB with the wheel.

They say a picture is worth a thousand words so I'll post a link after a word more. The focus is extremely touchy but once obtained on a bright star and home made bahtinov mask the lens holds rock solid for hours.

The pictures are with this lens on a Qsi583 but that has just about same sensor size as Canon 40D so you would end up with about 5+ degree field wide open at f/2.8 so tighter stars can be had by stopping down 1 stop but I have been happy so far so as not to double my exposure time for the added stop (life is a trade off ... always).

Here is a shot on my site but basically all shots there are this lens and camera. (site in in north so hope link works) I don't know how to post pics to Ice In Space.

http://astrospotter.zenfolio.com/p66...e09b#h3eabe09b

Good luck in whatever you end up using.

For stopping down the lens I use step-down rings which are cheap and very accurate. They are real cheap so you can easily pick up a few different sizes and do the stop down that way so that your stars remain perfectly round without the Canon 8-point stars from the 8-blade stop in canon lenses. With a step down to 37mm I can obtain very tight focus to do RGB shots without re-focus (seen in the M31 image on the same website). This too is tradeoff but not bad looking IMHO. See below

http://astrospotter.zenfolio.com/p31...57a0#h2a1e57a0
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  #33  
Old 27-10-2010, 04:35 AM
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While not wanting to cut Ashley out of the equation, I am too miserable to have something custom made, not unless there is absolutely no other way.
In my case a simple e bay buy found me a Pentax 67 to Sony DSLR adaptor (I have a Sony), and then got a mate to thread the inner section of the adaptor to accept a T thread. Then a simple male T thread section was threaded on, leaving the amount required sticking proud to accept the camera. Quirky as it sounds, the protruding T thread actually fits within the Sony adaptor if and when I have the bayonet section attached (4 very very small screws). This gives me the ability to use this one adaptor with both the CCD and the DSLR, via those minuscule 4 screws.
Gary
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  #34  
Old 27-10-2010, 09:05 AM
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I sold the 85 1.8 I had because I didn't like it at night.
Instead I'm using a 100mm F2.8 Macro and it works well.
The 70-200 are also great and the 200 F2.8L prime it's fantastic and cheap too.
The 550D is a great camera for astro, the HD video modes are very interesting for stacking purposes.
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  #35  
Old 31-10-2010, 02:24 PM
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Hi all, and thanks again for the input. I shall certainly go after those step-down rings now that I have seen the result of the internal diaphragm and its effect.

Well, I managed to rent the 70-200mm f4L lens for this weekend, and got out with it tonight. This is only an assessment, so the image is short on exposure, high on noise etc. But I am pleased with the lens.

The image here is 11 x 3 minutes, shot at f6.3, FL was 100mm, ISO800.

The image is 50% of its original size, and the lens had an UV filter on the front of it.

Instead of dark subtracting, I used a high dither rate, and used the power of CCDSTACK to remove the dark noise (it did an okay job).

I accept its noisy, and needs more exposure, but I like the lens. There is almost no cropping on this image except for minor alignment areas, and the stars are pretty good.

I have some more questions for you DSLR experts later.

Comments on this image very welcome.

cheers
Martin
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  #36  
Old 31-10-2010, 04:04 PM
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Octane (Humayun)
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Looks like you're up and running, Martin, top stuff.

I would imagine that f/5.6 would have been enough (closed down one stop).

Also, get rid of the UV filter on the lens! You'll only degrade the quality of the image by having light go through another layer of glass (typically, they're nowhere near the quality of the Canon glass, either).

Incidentally, I'm picking up the 70-200mm f/2.8L USM (non-IS) on Wednesday. I already have the 200mm f/2.8L II USM for astro, and, it is superb. Perhaps that's one you should look at, too.

H
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  #37  
Old 31-10-2010, 04:41 PM
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what about the 135mm f/2.
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  #38  
Old 31-10-2010, 05:04 PM
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The 135mm f/2L is superb.

But, I think Martin's after something a bit longer.

H
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  #39  
Old 01-11-2010, 06:00 AM
Martin Pugh
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Thanks guys.

actually - what I am looking for is a lens that can do (in priority order)

1. Milky Way, large asterism shots.
2. star trails
3. Meteorite showers.

So, I think about 100mm is good for Milky Way, but think that about 200mm is optimum for star trails.

100mm is probably too long for meteorite showers.

So, can 1 thru 3 be done with a single lens? Probably a zoom lens like 70-200mm would cut it?

any other thoughts?
cheers
Martin
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  #40  
Old 02-11-2010, 12:51 AM
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Martin: Very nice image!!

The problem is that a zoom lens won't be as fast as a prime for the same price. You can get a 70-200 F2.8L II lens but is very expensive.

I'd consider:

The 100mm F2 lens is really cheap and underrated, if you don't shoot macro the F2 aperture at 100mm really works nice for astro.

The 200mm F2.8 L II prime is also cheap and has excellent IQ.

I think 100mm is kind of large for the Milky Way but I'm not sure what kind of MW shots you like to do, to get a good span of the MW I'm using focals from 14 to 28mm on my 5DII.
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