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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

Example with a 90mm Maksutov-Cassegrain type scope (1 Viewer)

Yep they are impressive - thank heavens for birds that sit still ;)

So, regarding diameters, can i assume the apertures get worse as the diameter gets larger ?

EG .. 90mm Mak Cass would have wider aperture than 130mm Mak Cass. In which case, for those interesetd in trying out these scopes, it may be sensible in sticking to the bottom end range of the available diameters, like 90mm ?
 
Thanks for posting that link Jason. I've watched this fellows posts using a variety of Mak-Cass type scopes for years. He has some impressive images. As several people have pointed out these scopes have limitations. When I first started digiscoping, I was using lower-end spotters that were decent visually, but had severe problems with CA when digiscoping. I was just so happy when I finally got one of these Maks and could get some sharp CA-free images. I could control contrast much easier PP than I could a bleary photo with a bunch of purple and green fringing even if I could only take shots in really good light. Now, you can get a pretty good ED refractor for close to the same price as a good mak-cass scope, but they're still fun to play with.
 
Musoman said:
Yep they are impressive - thank heavens for birds that sit still ;)

So, regarding diameters, can i assume the apertures get worse as the diameter gets larger ?

EG .. 90mm Mak Cass would have wider aperture than 130mm Mak Cass. In which case, for those interesetd in trying out these scopes, it may be sensible in sticking to the bottom end range of the available diameters, like 90mm ?
Click to expand...

I had a 127mm Orion Mak Cass (MCT) some years ago, and it was ƒ12, so that rule doesn't necessarily apply. Intes Micro makes some of the best commercially available MCT's, and they have ƒ10 scopes at both 127mm and 152mm of diameter.
 
One reason to like MCT's is if you go big, you can get serious distance...sharpshooting distance...without CA or image breakdown. The Orion 180mm Maksutov Cassegrain has a FL of 2700mm!! Although it is a relatively slow ƒ15 scope/lens, it provides the same distance as a 600mm 1:4 lens with two 2x TC's stacked. At that point, the MCT will far outpace the pro grade prime. Of course, at that magnification, you better hope the atmosphere isn't full of turbulence.
 
bluedubius said:
Thanks for posting that link Jason. I've watched this fellows posts using a variety of Mak-Cass type scopes for years. He has some impressive images. As several people have pointed out these scopes have limitations. When I first started digiscoping, I was using lower-end spotters that were decent visually, but had severe problems with CA when digiscoping. I was just so happy when I finally got one of these Maks and could get some sharp CA-free images. I could control contrast much easier PP than I could a bleary photo with a bunch of purple and green fringing even if I could only take shots in really good light. Now, you can get a pretty good ED refractor for close to the same price as a good mak-cass scope, but they're still fun to play with.
Click to expand...

I agree, MCT's are great scopes. I like them mainly because they are different. But having spent many nights looking at Jupiter and Saturn through one, at magnifications well above 250x, I can attest to the inherently sharp design.
 
More informative posts Jason - cheers.

So how did you personally find trying to shoot birds with such high apertures like f10, f12 etc. Did you only take your scope out on sunny days and avoid late afternoon / evening low light scenarios ?
 
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First off, I don't shoot through astro scopes very often. I do shoot ƒ8/ƒ9 regularly in poor light (cloudy, early morning, etc...) with a Sigma 150-500. I am one of the few (it seems) shooters who really has little problem with pushing the heck out of my ISO. Noise just doesn't bother me all that much. It helps that I shoot with a Canon, a brand notorious for better noise processing. Still if my lens was sharper at higher apertures (ƒ10-ƒ16) I gander I would shoot that high regularly in mediocre light with ISO values between 1600 and 3200. So if I had a 180mm ƒ15 MCT I might do the same. It sure might come in handy for the RTH's and RSH's that frequent my back yard, but never come closer than 100-150 ft. :)
 
Fowl Mouth said:
Camera specific mirror lenses and astronomical Cassegrain style mirror telescopes aren't in the same league optically. While I agree that mirror lenses tend to leave much to be desired with regards to resolution, almost every astronomical Maksutov Cassegrain built in the last 30 years is 1/3 wave lambda or better, which means far higher surface polish quality than even the best professional grade camera lenses.

Additionally, and I'm actually not sure of the exact measurements, but looking at an image of a lens such as the Tammy SP-500, it appears that the central obstruction is close to 40-45% of the objective diameter. That much obstruction is contrast and resolution robbing. Mak Cass scopes seldom go above 35%, and some as low as 25%. With smaller sizes like this resolution is less impacted. While contrast may remain lackluster, we thankfully have plenty of software options to help correct this.
Click to expand...

Thanks Jason for enlightening me on this. The Tammy being a midget compared to the MCT are of course not in the same league. The Tammy also combine mirror and lens (4 elements if I'm not mistaken) thus still got some CA.

Thanks for linking the Bald Eagle gallery. Really opened my eye. Some of the shots are cropped though not so much, are still stunning.
 
Musoman said:
Yep they are impressive - thank heavens for birds that sit still ;)

So, regarding diameters, can i assume the apertures get worse as the diameter gets larger ?

EG .. 90mm Mak Cass would have wider aperture than 130mm Mak Cass. In which case, for those interesetd in trying out these scopes, it may be sensible in sticking to the bottom end range of the available diameters, like 90mm ?
Click to expand...

Pete, I think I am reading your mind.... Your next project???? LOL
 
:smoke:

I have little money anymore to experiment Al, so not yet. Its very interesting to read about the Mak Cass scopes though.

Maybe in the future, but it seems the quality Mak Cass scopes are not cheap.
I looked at the Intes Micro russian models and the smallest Alter M500 ( 127mm / f10 / 1270mm focal length ) was nearly £800

Ok, its incredibly cheap compared to the top Canon L glass like the 600mm f4 and 800mm f5.6 but when you are used to only spending £250 / £300 on scopes like my current SW 120 and previous SW 80ED, £800 seems like another league

http://www.intes.su/goode.aspx?d=1
 
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alphan said:
Thanks Jason for enlightening me on this. The Tammy being a midget compared to the MCT are of course not in the same league. The Tammy also combine mirror and lens (4 elements if I'm not mistaken) thus still got some CA.

Thanks for linking the Bald Eagle gallery. Really opened my eye. Some of the shots are cropped though not so much, are still stunning.
Click to expand...

You're welcome, Alphan. And I hope I didn't come across as either pedantic or judgmental. I happen to build telescopes for visual astronomical use, so I tend to get a bit long winded on this subject. It's as big of a passion as birding is for me.

I think you are 100% correct with your assessment of the SP-500 and the effect of the extra elements..
 
Musoman said:
:smoke:

I have little money anymore to experiment Al, so not yet. Its very interesting to read about the Mak Cass scopes though.

Maybe in the future, but it seems the quality Mak Cass scopes are not cheap.
I looked at the Intes Micro russian models and the smallest Alter M500 ( 127mm / f10 / 1270mm focal length ) was nearly £800

Ok, its incredibly cheap compared to the top Canon L glass like the 600mm f4 and 800mm f5.6 but when you are used to only spending £250 / £300 on scopes like my current SW 120 and previous SW 80ED, £800 seems like another league

http://www.intes.su/goode.aspx?d=1
Click to expand...

This one here would be within your reach though quality would be downgraded.
http://www.telescope.com/control/te...rion-apex-127mm-maksutov-cassegrain-telescope

Thanks for the link to the "Clash of the Bantamweight Scopes". Very informative and eye opener.
 
Fowl Mouth said:
I happen to build telescopes for visual astronomical use, so I tend to get a bit long winded on this subject. It's as big of a passion as birding is for me.
Click to expand...


We are a bit out of topic here but I can't help it. With my 80ED and EP's, I am picking up a little interest in Astronomy too and would be interested in building a Dob for my girl. Can you advice which Dob would be comparatively equal to my 80ED refractor? So if I am to build one, it got to be a better one than my current scope.
 
Cheers for that link to the Orion Al. I think f12 would be just too narrow an aperture for me. The 1500mm+ focal length is huge, and maybe hard to control...what do you think ?

Mind you, i know you can fit some kind of focal reducer to get the aperture down to f6 or f7 ( thats a guess )
 
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alphan said:
We are a bit out of topic here but I can't help it. With my 80ED and EP's, I am picking up a little interest in Astronomy too and would be interested in building a Dob for my girl. Can you advice which Dob would be comparatively equal to my 80ED refractor? So if I am to build one, it got to be a better one than my current scope.
Click to expand...

I'll send a PM so as not to completely ambush the thread. :-O
 
There's a good website on this link with lots of Orion 150mm Mak bird images. All the photos are pretty good but do show the hazy low contrast that these scope suffer from in daylight.

http://www.billmajoros.com/photoalbum/categories/new/BigLens/index.html

This one on the same site shows a good example of donut bokeh, notice the rings in the foreground and background.

http://www.billmajoros.com/photoalbum/categories/new/BigLens/flycatcher-7.jpg

The scope he uses is around £100 more than an 80ED in the UK. Handy if you need 1800mm but I find around 900mm is what I use 90% of the time.

Paul.
 
lack of contrast

I agree that the images on the web-site taken by the Mak. Cass. do suffer from a certain dullness/flatness. . The reason behind the particular glare that causes the lack of contrast in a Cassegrain telescope, as opposed to a refractor is because it is inherent in the design of this type that all light, not just stray light, all light that enters the optical tube is of no use to the eyepiece whatsoever until it has been reflected back up the tube and then reflected back down again off the secondary mirror. This passage of light three times up and down the tube will cause more scatter of light within the scope than a refractor has to deal with. A light baffle on the front of the scope will not help to solve this particular problem with the cassegrain type of scope, other than keeping out off axis unwanted light, as it will on any telescope, because it is the very on-axis light that causes the bulk of the problem. Put simply, the eyepiece of a refractor is keen to receive the light from the objective straight away, whereas the eyepiece of the cassegrain type does not want anything to do with the light entering the system until it has passed up and down 3 times, and at each pass extra glare causing light will be entering the eyepiece. Tom
 
Thanks for the link, Paul. I had not seen this one. I have enough trouble hiking around with the Celestron 80ED or the ETX-90...can't imagine lugging that thing around! I purchased my Meade ETX-90 years ago on sale new for $399, at a time when you couldn't touch a short-tube ED refractor for that amount. I bought the Celestron 80ED new on sale at exactly the same price ($399) for digiscoping with an eyepiece and P & S camera. I saw your first post on using astro scopes without an eyepiece and a DSLR shortly after and you converted me :). Still like to tinker with the ETX though.
 
I agree with you, Tom. The twice bounced light path has more opportunity to pick up internal reflections off of the multiple components in a MCT. The light baffle at the front does take care of much of the issue, IME. But you are right, the primary mirror will throw scatter off of the mount edges. Although higher end MCT's (such as the aforementioned Intes Micro brand) typically provide ribbed internal baffles to help eliminate much of the scatter off of the primary mirror mount, as well as oblique angle scatter from the inside of the tube. It's not a perfect solution but, as in refractors, it does help. I doubt you'll find any examples of birding done with high end MCT's, though. I'm guessing most bird photographers looking to spend $1500-3000 USD on a lens are looking at big AF lenses or larger ED refractors. I estimate that most bird photography done with MCT's in general is accidental.
 
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