Refractor 4 inch Aperture and 900mm focal length... did I make the right choice?

[Maged]

Hi,

I'm just few months into astronomy and my first telescope is a refractor with 4 inch Aperture and 900 mm focal length. I was having the waw factor when I first saw the craters on the moon and Jupiter bands and moons, the Orion nebula was a killer. But, when I'm started to be more interested in deep sky objects (I'm talking Andromeda Galaxy and other not so feint objects) I started to suffer. When I started to take steps towards astro-photography after installing a motor drive to my mount, I was frustrated.

So I need help, is it lack of my experience and skills that I will gain over time or is it wrong equipment that I'm using (more aperture is needed??) ?

Thanks,

[happy-kat]

Hi

Why not start with imaging the Moon. Then try Jupiter. Both of these you can use a webcam to capture them.

What camera have you tried to use so far and what has been your frustration?

If me I would look to exhaust what you have already bought before deciding where next.

[rwilkey]

Hi there, the refractor you have chosen is great for visual use on the subjects you have chosen, DSO's are OK as is M31 Andromeda, and you should see many more, the focal ratio is f/9 and will give great clear views of planets, Moon, double stars and star clusters.  For the feinter DSO's a reflector is better, but over time you will be surprised at how much you can see with the refractor and some good targeted eyepieces.  As for AP, it is not so good, a smaller, short refractor is better.  If you plan AP then it would be best to have a read of Steve Richards book, 'Making Every Photon Count' here: http://www.firstlightoptics.com/books/making-every-photon-count-steve-richards.html

This is the bilble for AP.  Highly recommended.

[Maged]

Happy-Kat -  I'm using Canon 70D (prime focal to the telescope) and I get nice pictures of the moon, and not so nice pictures of Jupiter (It appears so small in the photos and details are not good, as I see during regular observation with the telescope). But when it comes to the Orion nebula for example I get distorted images (even after balancing everything on the mount, and as correct polar alignment as I can).

rwilkey - Thanks for the link, I will definitely check this book out

[Maged]

rwilkey - you mentioned  "good targeted eyepieces" can you please give me recommendations? 

I already have:

32mm Orion Sirius Plossl

25mm Orion Sirius Plossl

17mm Orion Sirius Plossl

32mm Orion Sirius Plossl

40mm Meade Super Plossl 

6mm TS Optics HR Planetary

Celestron Omni 2X Barlow Lens

Am I in good shape regarding eyepieces? 

Thanks

[ronin]

Planetary imaging is not the same as DSO imaging and neither are the same as  taking a photograph. Much confusion can be caused by the whole lot.

For planets the scope you have is likely a bit too short, whereas fo DSO's it is too long and for looking through it is pretty good.   Starting to get the idea?

Planets - people put a webcam on the scope and take a video, then feed the video into a package like Registax. Pick the "best" 200 frames and stack these then tweek the stacked image (use the wavelet thingys on the left) to get a final image. (Bit over simplifiedbut that is the general idea) Planets can be made bigger so many put a barlow in to get a bigger image.

Moon is simply bright enough to point scope+DSLR at it and go click - using a remote release to minimuse shake.

DSO's leave these alone for now. They are the bit that need work.

The plossls you have are fine, I might suggest a 10mm but that is about all.

You list two 32mm Sirius plossl's = typo or collecting them ? :confused:

I have two of quite a lot, bit of a strange tale.

4" scope is a nice start and you could likely never bother with anything else, f/9 is OK for minimal CA and eyepieces for it need not be costly, plossls as you have.

One thing is all you will see of M31 is the central core, not a problem of the scope but M31 is just too big to get it all in view. use binoculars to see "all" of it.

[Davey-T]

The 70D probably has the crop video facility, so you can video Jupiter at 640 X 480 using a 2 inch Barlow of some sort, I use a Televue Powermate but they are expensive.

Dave

[PeterCPC]

If you use Backyard EOS with your Canon you can have a 5X or even 10X zoom enabled.

Peter

[glowjet]

You do not say which of the 100mm f9 scopes you have acquired, SkyWatcher or Celestron ED scopes, they are able to be fitted with a .85 dedicated flattener/reducer which brings the f ratio down from f9 to f7.6 which is not perfect, but better suited to some DSO work, if you want to give it a try. Your first purchase should, never the less, be a copy of Making Every Photon Count, as already mentioned by Robin.

Is more aperture needed ? I think if you take a look at the forum imaging sections, and the many library of images taken by individual Astrophotographers and see what can be achieved with 80mm and 100mm refractors, the results are quite remarkable. If, on the other hand, you have a yearning to go for the faint fuzzy DSO, then you are into a different league altogether, where a large aperture reflector, a good solid stable tracking mount and digital imaging camera, are the order of the day, you will also need deep pockets and a lot of patience, enjoy

[Maged]

ronin - Thanks for your helpful comment, I will get the 10mm. and the two 32mm are a typo

[Maged]

Davey-T - about the Televue power mate are these barlow lenses with good quality ?

[John]

Davey-T - about the Televue power mate are these barlow lenses with good quality ?

They are superb but pretty expensive. They are not barlow lenses but have a similar effect. They don't affect the eye relief or focal point of the eyepiece like a barlow does though.

The Explore Scientific Focal Extenders are pretty similar in quality but a bit less expensive.

[Maged]

Davey-T yes my camera has the crop video option but I noted another problem which is that Registax does not work with .mov extension which is the only option in the canon 70d. any recommendations? 

[mikeDnight]

When I began in astronomy some 35 years ago a 4" refractor was a serious piece of kit, and the possessor of such an instrument was often looked on as being a truly serious observer. Looking back through old Sky & Telescope magazines from the 1950s to the 1970s a 4" Unitron refractor with equatorial mount could have set you back the price of a house. Its good to look back at facts like these as it helps us not to lose sight of just how fortunate the modern astronomer really is.

Today there are many observers and imagers who use top end 4" refractors. John Mallas back in the 1960s helped produce a classic book (The Messier Album), drawing all the M objects as he saw them through his 4" Unitron. Today observers such as Steve O'Meara has published a number of books on visual deep sky observing using his 4" short focus refractor, a Televue Genesis.

Its true that many modern day 4" refractor owners have spent hundreds, even thousands of pounds or dollars to acquire their dream 4". That might on the surface of it seem rather silly, considering much larger telescopes of different designs are available much cheaper. The question is WHY?

The answer isn't so simple but is partly because a 4" refractor is so versatile being able to offer both high power, high contrast and rich wide field views. A modern one is usually reasonably portable and easy to mount. It is also relatively maintainance free. They are also capable of packing a much more powerful punch than their size would lead some to believe.

For what it's worth I'd stick with the 4" for a while. Learn your way around the night sky, sketch what you see, you're probably seeing much more than you at first might imagine. If you can over time, try to acquire two or three really good eyepieces, as the scope will only perform as well as the eyepiece permits. And, try your scope alongside other scopes of different designs, possibly at a local astro group. You may be pleasantly surprised. Enjoy!

Mike

[Maged]

Mike your comment is very motivating. Thanks

[swag72]

I can only talk from an imaging point of view as I don't look through my scopes having done so less than a handful of times. As you did mention astrophotography then I think that what I am going to write will be of relvance, if not to you then perhaps others who search for this type of topic later down the line.

I started off my imaging with just this length scope - a 120ED Skywatcher - I was given this advice by a retailer and while I am sure that they felt they were giving me the very best of advice at that time, I certainly hope that they have now changed their ideas. I was new to imaging, having never done it before and figured that it couldn't be that difficult. Of course I wanted to see everything............ Probably needed to know that was impossible.

So fast forward onto DSO imaging and the scope was undoubtedly not the best choice. DSO's are generally pretty large and 900mm I felt was a real betwix and between focal length. It was too long for many of the larger targets and that was frustrating. Then it was just too short for small galaxies and what not during the galaxy season. I wish with all of my heart that I'd been recommended an 80mm scope. It is less demanding on a mount for starters that will give you a better chance to obtain and more importantly keep hard earned subs.

Have you got the right scope for astro imaging alone? In my opinion I would say no, but from your thread and replies you are not limiting yourself to imaging alone, so perhaps that opens up options that were never there for me. 

At the end of the day, what you use and what suits you is the best scope! Good luck and enjoy it

[Maged]

Sawg72 thanks for your comment. Actually I will borrow an 80mm refractor with 400mm focal length from a friend to try it. Do you think this will be a good scope for astrophotography? DSO targets like andromeda for example?

[happy-kat]

To get to know the processing steps why not put your canon with lens on your tripod and start with some wide field images and then try with say a 135mm or so lens on some bigger DSO targets like m42, m45. You will understand the imaging experience and be able to better judge where you want to go next or even if you like it.

[Maged]

I will try that

[RT65CB-SWL]

Davey-T yes my camera has the crop video option but I noted another problem which is that Registax does not work with .mov extension which is the only option in the canon 70d. any recommendations? 

There are movie converters that 'convert' .mov files to .avi files. How well the work though and whether you will loose any detail I do not know. Some freebie movie converters have a watermark across the display and once registered or for a paid version the watermark is removed.

Maybe worth searching www.sourceforge.net for something. I find it a good source for utility software.

[swag72]

Sawg72 thanks for your comment. Actually I will borrow an 80mm refractor with 400mm focal length from a friend to try it. Do you think this will be a good scope for astrophotography? DSO targets like andromeda for example?

I think that this is going to be a much better scope for the larger DSO's

[kens]

If you are thinking about astrophotography for DSOs then you also need to think about your mount just as much as (or even more than) the OTA. Astrophotography is very demanding on the mount.

Happy-kats suggestion to mount the DSLR onto your mount is a good one. You can start to learn about stacking and image processing and also what you need to do with your mount to get longer exposures.

You may well find it is the mount that is your limitation rather than the OTA. 

[Maged]

I will buy a tripod to the camera and try

[happy-kat]

Why not only buy two things.

I have assumed it was an eq mount that came with your telescope that you got motors for.

What you need to attach your camera to the tripod.

The book Making Every Proton Count.

[Maged]

Yes I have EQ mount for my telescope. So is it possible to attch the camera to the mount? I never thought about that