AstroTrac TT320
Moderator: SAC Committee
AstroTrac TT320
Here a few of my shots from the Burren using my brand new AstroTrac. I really haven't had much time, so I haven't even stacked or properly processed the images, so what I show here is only the tracking accuracy of the AstroTrac. I am very impressed with it. I had far more problems with focusing and with dew than with the AstroTrac.
Beehive Cluster, 180mm lens @f/5.6, 168s exposure. Notice how nice and round the stars are.
Saturn, 180mm lens @f/5.6, 30s exposure.
See more at My Flickr astro pages
Beehive Cluster, 180mm lens @f/5.6, 168s exposure. Notice how nice and round the stars are.
Saturn, 180mm lens @f/5.6, 30s exposure.
See more at My Flickr astro pages
Mikkel Bo Rasmussen
+55° 49' 28.38", +12° 4' 8.24"
+55° 49' 28.38", +12° 4' 8.24"
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- Posts: 2980
- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
I'm using the manual focus ring on the lens to focus. My 180mm lens is really smooth and the FOV with an 180mm is good for focusing. I had more problems with my 35mm lens. I couldn't judge anything through the viewfinder.
The right angle (RA) finder adds another focusing factor, but it is easy to judge the correct focus of the RA even if the lens is not focussed properly yet.
Here is another image -- 5 minutes exposure of M57 "Ring Nebula" in Constellation Lyra. Tracking is right on the money. I have to try longer exposures, but my Nikon D200 starts to get noisy (thermal) around five minutes, so stacking is a better option. But for fun, I'll try 10, 15, and 20 minutes exposures, just to see.
Now I lust for a 400mm or 600mm lens ...
The right angle (RA) finder adds another focusing factor, but it is easy to judge the correct focus of the RA even if the lens is not focussed properly yet.
Here is another image -- 5 minutes exposure of M57 "Ring Nebula" in Constellation Lyra. Tracking is right on the money. I have to try longer exposures, but my Nikon D200 starts to get noisy (thermal) around five minutes, so stacking is a better option. But for fun, I'll try 10, 15, and 20 minutes exposures, just to see.
Now I lust for a 400mm or 600mm lens ...
Mikkel Bo Rasmussen
+55° 49' 28.38", +12° 4' 8.24"
+55° 49' 28.38", +12° 4' 8.24"
- John O'Mahony
- Posts: 552
- Joined: Sun Aug 05, 2007 8:36 am
- Location: Limerick, Ireland
- Dave Lillis
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- Location: Limerick city
Good tracking there Mikkel, although it looks like the lens might have very slight chromatic abberation.
Dave L. on facebook, See my images in flickr
Carrying around my 20" obsession is going to kill me, but what a way to go.
Carrying around my 20" obsession is going to kill me, but what a way to go.
Yeah the lens does have some CA. I stopped down two stops (from f/2.8 max aperture to f/5.6) but I may have to stop down even more. But that makes it rather useless, if I have to stop down to f/8.
I'm looking at getting a Sigma 400mm f/5.6 APO for the AstroTrac. They sell used for around $400. The Sigmas have virtually no CA.
I'm looking at getting a Sigma 400mm f/5.6 APO for the AstroTrac. They sell used for around $400. The Sigmas have virtually no CA.
Mikkel Bo Rasmussen
+55° 49' 28.38", +12° 4' 8.24"
+55° 49' 28.38", +12° 4' 8.24"
Instead of a Sigma lens (which I would be able to use in daylight as well), I am thinking about a small APO refractor.
Do any of you have experience with APO refractors in the range 66mm to 80mm apeture?
Specifically, I'm looking at these:
William Optics 72mm
William Optics 80mm
Orion EON 72mm ED APO
Apochromatic Refractor 80mm OTA (FPL53 glass)
Do any of you have experience with APO refractors in the range 66mm to 80mm apeture?
Specifically, I'm looking at these:
William Optics 72mm
William Optics 80mm
Orion EON 72mm ED APO
Apochromatic Refractor 80mm OTA (FPL53 glass)
Mikkel Bo Rasmussen
+55° 49' 28.38", +12° 4' 8.24"
+55° 49' 28.38", +12° 4' 8.24"
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- Posts: 2980
- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
This just about explains it all
http://www.eanet.com/kodama/astro/equip ... /index.htm
(scroll down to ;
Gotcha! #1 -- Wrong Finder Magnification)
I love the line...
http://www.eanet.com/kodama/astro/equip ... /index.htm
(scroll down to ;
Gotcha! #1 -- Wrong Finder Magnification)
I love the line...
Indeed!These have the problem of incorrect magnification relative to the reticle. In my setup, the two stars end up sitting not in the gaps but on the lines closer to the center (indicated by red spots in the figure 3). If you don't know this, you'll undoubtedly have pulled out some hair trying to figure out why you just can't get the stars to fit.
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- Posts: 2980
- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
Frank Ryan wrote:Mikkel, i wonder have you noticed a problem with the polar scope?
I raised the issue on the astrotrac yahoo group and Richard replied
(to Roland, he seems to think he started the thread )
anyway,
He is essentially saying you can still use them with a 'modified' alignment procedure,
EG, ignore certain markings and
guesstimate 2nd & 3rd star positions relative to the alignment lines.
I have to say I feel a little miffed.
I'm also not happy that I should have to 'make do'
after paying a lot of cash for it.
I will email him and voice my concerns.
He seems like a really good guy and I'm sure the 'new alignment procedure' works fine for focal lengths no more than 200mm
but I want to go deeper if I can and I just don't want to be wasting my
time.
Hi Frank,
Sadly I haven't had time to unpack my AstroTrac yet, and the weather has not been too good lately either.
However, I do remember having the same kind of aligning problems with the polar scope, and I was also somewhat disappointed about it.
Sadly I haven't had time to unpack my AstroTrac yet, and the weather has not been too good lately either.
However, I do remember having the same kind of aligning problems with the polar scope, and I was also somewhat disappointed about it.
Mikkel Bo Rasmussen
+55° 49' 28.38", +12° 4' 8.24"
+55° 49' 28.38", +12° 4' 8.24"
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- Posts: 2980
- Joined: Sun Aug 05, 2007 2:45 am
- Location: Ballycasey, Co. Clare
Hey Mikkel.
The weather world wide is a disaster!
I've been in touch with Richard at Astrotrac and he has explained the issue
to me.
I'm not going to get too caught up in the fact that the gaps are incorrect
because he assures me that once they are on the lines it will be fine.
Any word yet on weather you can make it to WSP08?
The weather world wide is a disaster!
I've been in touch with Richard at Astrotrac and he has explained the issue
to me.
I'm not going to get too caught up in the fact that the gaps are incorrect
because he assures me that once they are on the lines it will be fine.
Any word yet on weather you can make it to WSP08?