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Old Monday 30th January 2017, 01:20   #1
inland
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Need advice for large diameter astroscopes

Hi everyone, (newbie in forum).

I must be a "rare bird" because I just read the Cango thread: "Astroscope, art of the past?" and still thinking about getting an astroscope.

It is a long story. I'm looking for a dual-use astroscope; astronomy (sometimes) and birding (the most). First, I was determined to buy a Televue 85S, but it seems they have been discontinued, and, here in Europe at least, the latest units are sold too expensive (3100 €). Then I saw your photos with ED 80, especially the Skywatcher 80/600. Definitely, this image quality is what I am looking for.

Later, came Cango with his debate on new apo lens 150-600 mms. And the doubts about whether to adquire a unique astroscope or several lens, returned to me.
As I see it, it would be appropriate for me to purchase a lens like Tamron SP 150-600mm f / 5-6.3 Di VC USD G2 for walking/traveling and perhaps a larger diameter astroscope (100-150 mms) for car based trips where weight is not a concern. In this way, these diameters would really be useful for its astronomical use in deep sky and also planetary.

I have seen that some of you use this large apertures for birding, like 102 APO 700mm. Some advice in these diameters?

Last edited by inland : Monday 30th January 2017 at 21:30.
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Old Tuesday 31st January 2017, 08:09   #2
DanC.Licks
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The various 150-600 superzooms can't touch the Image quality you will get from a good 600mm APO doublet or better yet, triplet scope. The AF is nice, but things like the Tamron are so weak on the long end that they would just be frustrating for anything other than close by subjects. Forget astro. Here as an example, my 600mm triplet against my Sigma 150-600 Sports, which is far sharper on the long end than the Tamron.
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So there is always a trade off. The sharpest lens in the world won't do you any good if the shot is not in focus, so maybe that smartest thing would be to get a used Sigma C or a Tamron (dime a dozen now used.... says something) for carry around, and get an 80/600 APO doublet or 90/600 triplet for astro.
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Old Tuesday 31st January 2017, 11:03   #3
inland
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Thanks a lot, Dan. These images is what i'm really was looking for. I agree, a super zoom sigma or tamron for walking and a triplet for astro is the correct equipment

What about the TS 90/600 Triplet for astroscoping? Does anyone have experience with this scope?
here an lab test of the optic:
http://astro-foren.de/index.php?thre...-fast-perfekt/
Two focal lenghts (600-450mm), It seems comparable with TV85 (Res. 1.29" /Limit value 12.3 mag). Maybe too weight, but thinking on base trips...

Last edited by inland : Tuesday 31st January 2017 at 11:05.
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Old Tuesday 31st January 2017, 18:43   #4
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That is what I have and it is excellent.
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Old Thursday 2nd February 2017, 11:01   #5
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Hi,

As Dan writes, and adding some words.

I myself have this scope, what I can see same glass/tube however fitted with a cheaper 3" Crayford focuser and the price tag was lower when I purchased it back in 2013: http://www.teleskop-express.de/shop/...A-Focuser.html

It's a triplet, 102mm aperture, F/7 so around 700mm focal length. I am extremely pleased with the IQ it delivers. The drawback is the weight but I am fit and used to carry it. I use it on a CF tripod with two-way gimbal head and also with bean bag as support. It's possible to use from within the car using the window/door as support however a tad tricky due to the length. Depends on how wide car you have and the viewfinder options. When shooting from car or at low/ground perspective I prefer to use the LCD over the electronic viewfinder. (I use Olympus E-M5/E-M1).

Reach is nice to have but 700mm is sometimes "too much", depending on the situation and motif. If I had to pick one tool only I would probably go for 600 or 500mm and sacrifice focal length for speed. Now I have two scopes, the other is a 480mm that is really nice for closer action, so the gap is filled.

Some photos taken with the scope are on display in the "Gallery" section on the forum http://www.birdforum.net/showthread.php?t=194789. Not all taken with this scope, please check the body text. There are some older ones as well taken with SW80 ED.

What camera system are you planning to use by the way?
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Old Thursday 2nd February 2017, 20:24   #6
inland
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-Wow! -Tord these shots are awesome, I hope someday I could get something like this.

As I told to DanC, lately I'm thinking of acquiring a 150-600 mm lens (probably used) for hiking and fast moving images and a TS 90/600 ED TS for car base trips:

http://www.teleskop-express.de/shop/...positions.html

There is no space problem with my camper van. You could even install tripod inside it!

Probably the TS 90/600 (4 kgs) plus a Nikon D7000 will be near the upper limit of weight for my tripod Ultralyt WT6907 (max. 7 kgs) and a diameter of 90 mm at the lower limit for short exposure times for astrophotography .

It seems that this astroscope has a retractable dewcap - it decreases the length of the tube to only 450 mm, so there are three different focus positions from the focus, but I'm not sure if this possibility needs a flattener or anything else. A flattener will be needed for astrophotography, but maybe not for digiscoping with a non-full frame camera (TS 2.5 "flatter costs € 290.) Perhaps the retractable dewcap also avoids the use of an extension tube .

I must investigate all this.
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Old Friday 3rd February 2017, 07:16   #7
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The dew cap is simply a lens hood. It has no effect on the focal length. You do not need a flattener for terrestrial stuff, and with a crop sensor, I doubt you would need it for astro, though I can't guarantee that..
The pictures in this album were all taken with a D7000, the first half, up to DSC_8675 (Bee-earter and Starlings) with a Skywatcher 80/600 doublet (BiF Bee-eaters with an old Nikon 400/5.6), and the second half with my 90/600 triplet.
Don't know your tripod, but you might consider a gimbal for birds. Makes life much easier.
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Old Saturday 4th February 2017, 11:58   #8
inland
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Sorry I confused dewcap as a possibility of modular tube!!
Just one more question. Do you need to use a extension tube?
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Old Saturday 4th February 2017, 17:50   #9
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You will need an extension tube to bring the camera sensor on the focusing plane. 80 mm length is usually about right. Too long you will loss ability to focus at infinity.
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