Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Is it cheaper/easier to start with film?

This topic has been archived. This means that you cannot reply to this topic.
55 replies to this topic

#1 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 15 October 2006 - 06:30 PM

I've never done astrophotography and am even pretty new to astronomy with an SCT but am a quick learner. I've looked at CCD imagers but after asking some questions found that on a 10" SCT with an F/10 focal length the field of view is quite tiny with most lower priced CCD imagers and even with a focal reducer it seems still small to me. I used the CCDCalc software to check what the field of view would be. Anyhow, I'm wondering if regular film is cheaper and/or easier to start with in astro-imaging. Looking at some of the cameras mentioned they can be had for really cheap. I know I'll need a wedge, but that aside 35mm film should give a much large field of view correct? Like, if I were to image the Orion Nebula I should get far more of it in the view than a CCD imager such as the Meade and Orion models? Lastly, with film do most people just do longer exposures or do people still take multiple shots and stack them in a software like Registax - and if so why rather than just do a longer exposure? Thanks.


Rev.

#2 microbes

microbes

    Apollo

  • *****
  • Posts: 1,217
  • Joined: 12 Dec 2004

Posted 15 October 2006 - 07:31 PM

if I were to image the Orion Nebula I should get far more of it in the view than a CCD imager such as the Meade and Orion models?



With a 10 inch f/10 you can fit about 95% of the orion nebula in the frame of a 35mm camera. Go here to make the calculations (and to down load the CCD calculator, a good program to compute how something is framed):

http://www.wodaski.c...ck_a_camera.htm

Compared to a Meade DSI the FOV is much larger with a 35mm camera by a huge margin.

I'm wondering if regular film is cheaper and/or easier to start with in astro-imaging.



Certainly cheaper to get started. Beside the lower camera cost, you don't need a lap top. Easier? I don't really think it's easier, you don't get instant feedback like you get with a CCD.

#3 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 15 October 2006 - 07:46 PM

Easier? I don't really think it's easier, you don't get instant feedback like you get with a CCD.


Heh, excellent point! Luckily I'm more concerned with FOV :)


Rev.

#4 redvis

redvis

    Apollo

  • *****
  • Posts: 1,178
  • Joined: 30 Jan 2005

Posted 15 October 2006 - 07:52 PM

35mm film is an excellent way to start astrophotography. I started with digital and didn't like all the fuss - dark frames, bias frames, flat frames, etc. All that extra shooting seemed to me to negate the perceived benefits of instantaneous response. So I went film and love it. The most important thing is to get to a nice dark sky site!

Pick up an old camera and give it a shot! You'll only be out a few dollars and you can use that wedge for CCD/DSLR astrophotography if you decide to go that route.

You can stack your images in Registar or even Registax for film. The reason you can't really do multiple short exposures is because film records light in a non-linear way. You stack film shots to reduce noise/grain in your photos making them look very nice and very smooth. My new technique is going to be shooting fewer objects each night but shooting each object twice so that I can stack the two shots when I'm done.

Let us know if you have any more questions!

Cameran

#5 Suk Lee

Suk Lee

    Aurora

  • *****
  • Posts: 4,566
  • Joined: 07 Oct 2003

Posted 15 October 2006 - 08:41 PM

There's another factor - you can get wonderful widefield shots with 35mm easier than with CCD. Slap your 35mm camera with a 50mm lense on an inexpensive mount or a barndoor, and you can capture beautiful widefields with hardly any investment.

High res shots of galaxies on CCD are technically impressive, but IMHO a nice widefield vista is much more beautiful.

Cheers,
Suk

#6 s58y

s58y

    Fly Me to the Moon

  • -----
  • Posts: 6,519
  • Joined: 12 Dec 2004

Posted 15 October 2006 - 10:12 PM

I started with digital and didn't like all the fuss - dark frames, bias frames, flat frames, etc.



Wouldn't you still need flat frames, even with film (to correct for vignetting, etc.) Maybe there's less dust with film, though? Or does the non-linear nature of film cause problems applying flat frames?

#7 ClownFish

ClownFish

    Fly Me to the Moon

  • *****
  • Posts: 6,588
  • Joined: 26 Apr 2005

Posted 16 October 2006 - 12:31 AM

To answer your question, "is it cheaper to start with film?"

Absolutely! I have found film imaging to be significantly less expensive than digital, when comparing similar results. Also, film is more forgiving of error, so a cheaper mount can be used.

But you have an f/10 system, which is virtually impossible to use with film. You'll need to cut that down a bunch with a focal reducer. Even then, an F/6 system will not be easy, as it will require a MUCH longer exposure than a system at f/4 or f/5. You will definitely need a focal reducer. In the meantime, I suggest you use the SCT as a guidescope and piggyback a 13mm or 200mm telephoto lens on your scope. This will give you lots of astrophotos, and is very easy to do compared with prime focus work.

But.. since this is as good a post as any, I will address my overall view of film imaging. Here's the argument I often hear: "Film images are not as good as CCD images!"

While they are no longer as POPULAR, that are certainly as good. If you compare similar PRICED setups, film will outperform CCD imagers in image quality, resolution, and field of view. While expensive dedicated CCD imagers can be purchased that rival or out-perform film, their cost is far greater than a typical film setup. Also, MOST amateur astrophotographers do not buy these very expensive hi-end digital CCD cameras. So when comparing the a FILM setup with the average CCD astrophotographer setup, at similar costs, film can equal or surpass them. This is NOT to say that film photography is superior to all CCD images.. not at all! There are specific areas where CCD imaging can easily outperform film, such as imaging in light polluted skies and during a full moon. Also, the much shorter INDIVIDUAL exposures of CCD imaging require a less demanding effort on the part of the photographer, especially when combined with an autoguider setup. And when shooting high magnification shots of BRIGHT objects, such as the moon or planets, CCD imagers and even web cams can easily surpass the quality of film. For DSO work, you will find film an excellent medium though, with a lot lower start-up cost.

But it is interesting to compare actual results between the two platforms. While I wanted to show a comparison between the BEST images from both platforms at comparable priced setups, I could not find a single one that even came close to having similar results. When choosing a system on price, there just is no comparison, film results exceed CCD in every respect (for deep sky work). So here I have found some exceptional CCD images but the cost of these systems far exceed the film system. The two images (below) are excellent astrophotographic images.

In the photos on the LEFT, they were taken with a TAK FSQ 106N APO telescope, EM-11 mount, and an SBIG ST-10XME camera. It was total of 2 1/2 hours of exposure. The total cost of this setup was over $14,000.

The images on the RIGHT were single 40 minute exposures with a stock Meade LXD75 8" Schmidt Newtonian, a 26-year old Olympus OM-1 camera and $7 worth of film (Fuji Provia 400F). Total cost of this setup was under $1,500. You can see a difference in the enlarged versions.. but is this difference worth over $12,000? That's up to you.

Posted Image

From a dark site, film imaging can also be as easy as point and shoot (well, point, guide and shoot). This is ONE single exposure, with absolutely zero computer post processing. No stacking, no bias, no flats, no stretching, or other color balance. This is straight from the developer, it doesn't get any easier than that.

Posted Image

And just look at that field of view! Here is a comparison of the Meade DSI to 35mm film. Mind you, medium format film is even MUCH MUCH larger. This is a single 40 minute shot of M31, taken with the Meade SN8 and 35mm film (Fuji 400F Provia). The center grey portion is the view through the DSI. See a difference?

Posted Image

You asked why do multiple exposures than just do one long exposure? Well, you CAN do multiple exposures to reduce noise, but there isn't much noise in film. Since film is not linear, you need long exposures to capture fainter details. This has both an advantage and disadvantage.

CCD users think 5 minute exposures are long.
FILM users think 90 minutes is long.

An average DEEP SKY shot with film is from 30 to 60 minutes. The average DSO with a CCD is from 1 to 3 minutes per exposure. but repeated many many times.

CCD: By having short sub-exposures, you can toss out bad subs, and only keep the best ones for your final print. Also, since your subs are so short, errors in polar alignment are not as evident.

FILM: By using less sensitive film (vs CCD) you can correct errors on the fly and they will not show up on the final print. I manually guide, and can guide out errors that would definitely be a problem with a much more sensitive CCD. I'm good at guiding, but not THAT good. Also, I have bumped the scope and knocked the guide-star way out of the field, quickly found it again, and continued with no ill effects. This is certainly an advantage of manual guiding too, as an auto-guider would have been lost, and had to be reset.

Anyway, I hope people don't misunderstand me. I'm not saying one technique is better than any other. This is a HOBBY and is supposed to be FUN. If you enjoy working with film, do it. If you enjoy working with hi-tech CCD imagers, do it. In the end, YOU have to be pleased, no one else. My goal here is to clear up misconceptions about film astrophotography, since few commercial businesses will. Why should they.. there's no profit in it? I'm sure if Meade was selling film cameras instead of digital cameras, they would have lots of details of film imaging on their site!

(It's interesting to note how the Meade SN8 uses an oversized secondary, that PERFECTLY illuminates a 35mm FILM frame, yet is wasted on a smaller CCD camera. They don't mention that in their catalog either anymore either.)

CF

#8 ZachK

ZachK

    Viking 1

  • -----
  • Posts: 840
  • Joined: 20 Aug 2005

Posted 16 October 2006 - 02:18 AM

Another plus about doing film. Many of the cameras people here use are old. I'm using a Rollei that was probably made in the 50's and it does a great job. So while you could go out and buy all new stuff and spend a lot of money you can often save a lot by looking around for used stuff. Chances are you know someone who has an old 35mm SLR that would be perfect, and they haven't used it in 5 years as they upgraded to a digital. Thats how I got my setup, a neighbor had some old cameras that she had not touched in years. She was happy to give me a Pentax K-1000 and a Medium format Rollei for nothing (and a Bogen 3036 tripod).

Pretty much any old manual 35mm SLR will work so look around, you may be able to pick up a working one for almost nothing from a friend or neighbor. And the basic film formats (35mm, 120 etc) have not changed in a long time so an old camera can use modern films.

#9 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 16 October 2006 - 09:59 AM

But you have an f/10 system, which is virtually impossible to use with film. You'll need to cut that down a bunch with a focal reducer. Even then, an F/6 system will not be easy, as it will require a MUCH longer exposure than a system at f/4 or f/5. You will definitely need a focal reducer.


Hmmm, now I'm confused :) One of the primary reasons, outside of cost, with looking at film is that 35mm provides a much larger field compared to a CCD which I always see people saying a focal reducer is a must for CCD imaging. So what is the reason I would need one for my scope? I'm still a total noob so sorry for having to ask. Also, why would the exposure times need to be longer? I've seen a number of photos of Meade LX's with cameras attached, how are those people making film imaging achievable with their F/10 scopes? Thanks for all the great info in your post by the way!


Rev.

#10 lawrie

lawrie

    Vanguard

  • *****
  • Posts: 2,217
  • Joined: 31 Jan 2006

Posted 16 October 2006 - 10:29 AM

The FOV (field of view) through the f/10 is small, when you add a focal reducer, it reduces the focal ratio, this increases the FOV, it also flattens some of the curvature of the mirror that may be seen in the image.
If you download the program in the second response of this thread you will be able to see how a FR effects different imagers.
One of the best ways to start astro imaging, IMHO, is just as clownfish suggests, piggyback photography, adding the camera to your scope and guiding with the scope, with this system you will learn how to guide, where these items are in the sky, and get results that will help you learn and go further with this hobby
I don't know if you can use a 3.3 focal reducer with film, maybe someone can answer that question.

#11 microbes

microbes

    Apollo

  • *****
  • Posts: 1,217
  • Joined: 12 Dec 2004

Posted 16 October 2006 - 10:57 AM

So what is the reason I would need one for my scope? I'm still a total noob so sorry for having to ask.



I'm going to differ with CF just a little. I think you could probably do some shots of brighter objects at f/10. But f/10 is a slow slow focal ratio, and dimmer objects would require way to long of exposures.


Coveington's software says that a bright nebula such as m-42, m-27, etc. would take 40 minutes in a 10 inch f/10 scope with 200 speed film. Not un-doable if your mount tracks well, but if you used a .63 focal reducer you could cut that time down to 12 minutes.

If you moved to a 800 speed film, the times would be 7 minutes and 2 minutes. You won't get the best pictures on 800 speed film because of the larger grain, and with your equipment I would try to shoot with 200 speed slide film.

Obviously, the shorter the exposure time, the easier it is to prevent tracking errors.

But here's the kicker: On a dimmer target such as the outer regions of the average galaxy, even with 800 speed film covington say's that thru a f/10 10 inch scope the exposure time would be "Excessively long". But at f/3.3 you can get that time down to 1 hour 20 minutes. A long exposure to be sure, but doable if you can track well.

Another example, the core of an average galaxy. On 200 speed film at f/10 - 3 hours 40 minutes. At f/6.3 - 1 hour 12 minutes. At f/3.3 - 14 minutes. Obviously, your tracking would have to be totally spot on to go 3 hours 40 minutes at 2500 mm without errors. That length of time will tax even the best mount. But 14 minutes at 850mm focal length? Much more realistic.

To make a long story short, at f/10 some targets are possible, others are going to be impossible. And some will be very very difficult even with the best equipment.

#12 ClownFish

ClownFish

    Fly Me to the Moon

  • *****
  • Posts: 6,588
  • Joined: 26 Apr 2005

Posted 16 October 2006 - 11:09 AM

The 3.3 reducer will not work well with 35mm film.

Back to the question about why I did suggest film with the F/10 SCT without a reducer.

Film is not nearly as sensitive as CCD imagers, and the sensitivity is NOT linear. This means that if you double the subject brightness with a CCD imager you can 1/2 the exposure time. But with film that is not how it works. With film you need as bright a subject as you can get, and that's where a focal reducer helps. A reducer (going from f/10 to f/6 for example) creates a much brighter image. It's just like on a camera when you go from a high F/Stop to a lower number the required exposure times become shorter.

Film suffers from RECIPROCITY FAILURE. This means that film tends to loose faint data during an exposure. Some films are far worse than others, and in all cases, the faster the ASA rating the worse this loss is. This is why Kodak E200 (ASA 200) is much slower than ASA 1600 film, but after a long time exposure the E200 is still able to record faint light while the ASA 1600 has almost stopped recording. So after only 8 minutes of exposure the "slower" 200 ASA film continues to capture faint details vs the ASA 1600! Plus you get the added benefit of a MUChH smaller grain and higher contrast.

All those people using an LX90 with film are using a reducer (unless they are shooting bright objects like the moon or planets).

I do not have the exact numbers, but it would be like this:
When imaging a faint DSO and comparing the same density on the negative, a 20 minute exposure taken at f/4 would need about 4 hours at f/10!

CF

#13 microbes

microbes

    Apollo

  • *****
  • Posts: 1,217
  • Joined: 12 Dec 2004

Posted 16 October 2006 - 11:12 AM

Here is where you can download Covington's exposure caculator that I was running numbers on:

http://www.covington.../astrosoft.html

This is another really great piece of free software. I've found it to be pretty darn accurate, and I use it every time I get ready to shoot a roll of film. To me it's a "must have" if you are going to shoot film.

#14 microbes

microbes

    Apollo

  • *****
  • Posts: 1,217
  • Joined: 12 Dec 2004

Posted 16 October 2006 - 11:22 AM

The 3.3 reducer will not work well with 35mm film.



Not that I need to use a focal reducer with my little 62X300 scope, but can I ask why? Does it vignet real bad, or induce to much curvature or what?

#15 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 16 October 2006 - 12:01 PM

Yeah I've already downloaded that software, part of the reason why I'm asking so many questions :) When I put in my scope parameters and choose 35mm film it looks like Orion fits quite nicely in the frame. I was completely unfamiliar with the fact that higher focal lengths require more exposure time. So, last question I guess would be... what is the right focal reducer number I should be looking at being 3.3 was said as being bad for film? Maybe 6.3?


Rev.

#16 microbes

microbes

    Apollo

  • *****
  • Posts: 1,217
  • Joined: 12 Dec 2004

Posted 16 October 2006 - 01:24 PM

higher focal lengths require more exposure time.



Exposure time is determined by focal ratio, not focal length. A 20 inch scope with the same focal length as yours would be an f/5, and require much less exposure time by a large margin.

Focal length determines image scale, a 20 inch f/5 scope would produce the exact same image scale as your 10 inch f/10. (a 20 inch scope would need one heck of mount to do long exposure shots, but that's another subject)

#17 ClownFish

ClownFish

    Fly Me to the Moon

  • *****
  • Posts: 6,588
  • Joined: 26 Apr 2005

Posted 16 October 2006 - 02:27 PM

Put me down for one of those! ;)

CF

#18 UrbanStarSeeker

UrbanStarSeeker

    Messenger

  • -----
  • Posts: 429
  • Joined: 23 Apr 2006

Posted 16 October 2006 - 04:21 PM

Is it easier? Depends on what you're good at. If you're good with computers and image processing, then I would say that digital is probably easier. Focusing with film can be a challenge since you don't have instant feedback unless you've got something like a knife-edge focuser. I tried prime focus photography (ie directly through the telescope) with film, got the pictures developed and got nothing worth having. I got the same result trying piggyback work (skyglow killed those). I ordered a digital SLR the next day, and I haven't looked back.

Is it cheaper? Again, it depends on how you count. The initial layout is clearly cheaper for film, but you also have to factor in the on-going costs of film and processing. Using CF's figure of $7 for that one image, once you take about 70 images, you've spent the cost of a Canon Digitial Rebel XT just in the on-going cost and not including the cost of your camera. Going digital means you have almost $0 of on-going costs. So with digital, you've only got the cost of your equipment and software, and the software I use is all either cheap (<$50) or free.

The option everyone here seems to be overlooking is the digital SLR. They're relatively inexpensive (ie can be had for $500 or so), can be used for daytime work like the film SLR, can still be easily used for piggyback work like CF suggested, can work without a laptop, and they still have a relatively large sensor. DSLRs come with a lot of the advantages and disadvantages of both formats. Most don't have a sensor quite as large as film (27mm vs 43mm) but have a much larger sensor than most inexpensive CCDs (DSI sensor ~8mm vs 27mm for a typical DSLR). You still have to take and combine dark frames. You have the option of using flat frames, which I'm not exactly sure how you would make that correction with film, but it would certainly be a problem if you didn't have a fully-illuminated frame from your telescope (I don't believe you would with your SCT).

Another thing to keep in mind is if you're looking for a wide field-of-view, then an SCT is not the right scope for the job. You will almost certainly get a significant amount of vignetting on the SCT. I even get a little vignetting on my 8" f/5 newtonian on the 27mm frame of my DSLR, so much of that film area may go to waste. Also your example of the Orion nebula is a bit of a one-off case. The vast majority of objects are much smaller and will fit even fit on a DSI frame. There are other large objects out there, but your 'scope is not well suited to capture them. For large objects/wide-fields you're much better off with a small APO refractor.

With all that said, to demonstrate the field of view of a DSLR at 1000mm focal length, here is my full-frame shot of the orion nebula. Obviously not the greatest shot in the world, but it was taken on only my second night out with the equipment. The camera cost was a Canon Digital Rebel XT that cost $700, the telescope was a Celestron G8-N (8" f/5 Newtonian) and the mount was an older model CG5 with dual axis drive. The scope/mount combo was only $500 new. There was no guiding, and no laptop used to take this image.

Allan

Attached Thumbnails

  • 1201000-M42.jpg


#19 ClownFish

ClownFish

    Fly Me to the Moon

  • *****
  • Posts: 6,588
  • Joined: 26 Apr 2005

Posted 16 October 2006 - 04:35 PM

Good post Allan. Nice image for your second night out!

I will add that I did not pay $7 for one shot as you mentioned. It was $7 for a roll of film, and I have 10 shots on that roll that I kept. In all the images I have in my gallery here, they are from only 3 rolls of film.

DSLR's are fairly new, so I can't say for sure what the life expectancy is. If you keep the same DSLR for 5 years, then yes, it will be cheaper in the long run. My OM-1 is 26 years old and counting. So far, from what I've seen, many DSLR users have jumped from one camera to another within 4 years. Once you do that, this cost advantage goes out the window.

Anyways, I agree that IF you have the money I would suggest you grab a modified DSLR, but the original poster here seemed to be looking for a CHEAP alternative to a CCD imager. A DSLR does not fit that bill.

As far as the SCT for astrophotography, I agree that the shorter scope would make a better platform when starting out. The FORK mount would have to go (for me) as it is too limiting (can't change OTA).

CF

#20 redvis

redvis

    Apollo

  • *****
  • Posts: 1,178
  • Joined: 30 Jan 2005

Posted 16 October 2006 - 06:59 PM

Well if you're good with computers then you should also use film. If you take a look at my NGC6995 shot in the forum you'll have access to a raw film scan and my finished result. There is still computer work involved with film if you want it. I personally like the challenge.

As for focusing, there is instant feedback with film. It's called the viewfinder. The viewfinders on DSLRs are intentionally dimmer and smaller (I believe there was a whole article on this in a recent issue of some photography magazine) and it makes their viewfinders less effective for focusing. For my shots I just look through the viewfinder and focus. Pretty simple, and my focusing feedback is instant.

For the price of a DSLR you can get a Meade LXD75 mount with Autostar #497 used. Toss in about $20 for an old SLR and $4 for some E200 and you're good to go. If you want to see what kind of shots you can get on an LXD 75 mount you can see Clownfish's shots or mine in my gallery: http://www.heliographic.net/deepsky/

Don't forget that a DSLR will also need to be modified, voiding your warranty. Otherwise you'll only be able to pick up the brightest deep sky objects or have to do longer exposures than film to pick up faint objects.

A 24 exposure roll of E200 is $4. Developing is $7. So that's about $11 for 24 shots. That means it's $11 for 24 shots total. So, to equal the cost of a DSLR you would have to shoot 1,080 pictures. Ok, so figure that you're going to shoot probably 2-4 nights per month (let's choose 3 nights to be fair, and you all know that is a generous estimate due to weather!). So 3 nights, and figure about 5 shots per night with 1 hour exposures if you're lucky. So that's 15 shots per month assuming you have absolutely perfect weather. At that rate it would take you 72 months, or 6 years to equal the cost of a $500 DSLR. Something to keep in mind. Even if we change the numbers around you are looking at many years before you reach the cost of a DSLR. By that time you should know if you want to continue in astrophotography.
I tried to get "fast" results with digital. Then I realized it was a hobby and not a race. However, I have nothing against digital, I use it for my solar work and used to have SBIGs, DSIs, and modified DSLRs. For me the best bang for my buck and most fun has been with film. I'll see you in 6 years ;-)

Hope that helps!

Cameran

#21 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 16 October 2006 - 07:10 PM

As far as the SCT for astrophotography, I agree that the shorter scope would make a better platform when starting out.


But wouldn't it still be fine if I just bought an F/6.3 focal reducer and an equatorial wedge?


Rev.

#22 Rev2010

Rev2010

    Apollo

  • *****
  • topic starter
  • Posts: 1,131
  • Joined: 25 Sep 2006

Posted 16 October 2006 - 07:27 PM

As for focusing, there is instant feedback with film. It's called the viewfinder.


Can you focus just the same through a Canon OM-1?


Rev.

#23 redvis

redvis

    Apollo

  • *****
  • Posts: 1,178
  • Joined: 30 Jan 2005

Posted 16 October 2006 - 07:49 PM

Rev.,

I don't own an OM-1 but I know Clownfish does. He uses a knife-edge focuser which helps reach focus. You can use interchangeable view screens with the OM-1 to get a brighter view through the viewfinder and then use a varimagnifier (basically a right-angle finder for the viewfinder that doubles magnification) to reach focus.

Alternatively you can use a Stiletto Series IV knife edge focuser. They seem to work great (used mine once and it seemed to do the trick, but now I just use my viewfinder).

Clownfish will be able to give you a better answer, I know it! :)

Cameran

#24 ClownFish

ClownFish

    Fly Me to the Moon

  • *****
  • Posts: 6,588
  • Joined: 26 Apr 2005

Posted 16 October 2006 - 11:43 PM

The Olympus OM-1 does indeed have interchangeable focusing screens. I have one in mine that makes a nice bright matt field to focus on. You can do pretty well with a magnifier (Vari-Mag) that attaches to the camera but it takes a lot of practice and a good focuser on your scope. To speed things up, and to eliminate errors I bought an STI Stiletto which means you do not use the camera's focuser at all.

Yes, you can certainly use your Fork mounted SCT. But remember, you MUST guide your shots so you will either need an Off-Axis Guider or a short tube/ long focal length (Mak) guidescope. Some have had good results with the Mak, which may be your best bet. An OAG is a pain to use. The only downside to the Mak guidescope is the potential for flexure in the two systems due to the shifting mirrors. If you have a solid Mak and can lock the mirrors down on both the Mak and the SCT you may not have a problem.

CF

#25 Allaboutastro

Allaboutastro

    Mercury-Atlas

  • -----
  • Posts: 2,695
  • Joined: 10 Jan 2010

Posted 17 October 2006 - 12:12 AM

One issue that isn't discussed is the superior resolution and excellent S/N of CCDs as compared to film. This allows you to better match a CCD with appropriate optics to get the field of view you require without sacrificing much in the way of resoltion as compared to film.

In other words, you don't need a comparitively large chip to provide the field of views you need simply because CCDs are better candidates for focal reduction.

For example, a 10" SCT f/10 system (2500mm focal length) yields around 35' x 47' of sky coverage with 35mm film. But a relatively smaller CCD chip, like the KAF-2020 at 1600 x 1200 pixels at 7.4 microns, produces much larger field of view when appropriately mated with a shorter focal length apo refractor, such as the Tak FSQ-106 at 530mm...even a "regular" 4" f/8 apo with that chip provides a very similar FOV as the 10" f/10 SCT with 35mm film.
Because the focal lengths are shorter with the CCD system, and because the technology is there for much superior resolution and guiding techniques, the CCD/refractor combo would actually produce the sharper, more detailed image.

But the real issue is that shooting 2500mm focal lengths is very difficult to do, particularly with an f/10 system on film. That's a killer. I would suggest you come down a bit in focal length, and honestly, a 10" SCT f/6.3 isn't coming down enough, regardless of the medium.

For best results, I'd recommend going with a small apo refractor on a solid (if unspectacular) GEM...and I'd mate it to your choice of cameras, though I'd recommend the SBIG ST-2000xm at that point. Yes, such a system would cost in the areas of $3k to $4K, depending if you by used or not. However, that makes more sense to me than sinking tons of money into ways to make your current system better...and you'll still fall short of expectations due to the longish focal lengths.

Don't get me wrong...I'm a big fan of shooting film as a starting point, but in no way should anybody think that film can come close to competing with dedicated astro CCDs, or even modified DSLRs; however, film competes VERY well with unmodified DSLRs...and in fact, I like film better in that comparison.

So, if you want the best opportunity for success, whether with film or CCD, you'll need to come down in focal length...and at that point, it opens up a whole lot of cheaper CCD solutions.


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics