2010-07-29
2010-07-19
Review of the Nikon 180/2.8 ED Ai-S
I think this is one of the best value lenses out there for widefield astrophotography. Jerry Lodriguss has put up a review of this lens on his blog, "Catching the Light". Check out his site for his very clear articles and books on beginning astrophotography.
QHY8 reprise
In a previous post, I wrote about the trouble I had with my QHY8.
So, I spent a bit of time fiddling with the QHY8 getting the CCD square to the front plate. I adjusted the rear screws and was able to get the CCD square according to my measurements. But no matter how I changed the tension, I couldn't see any difference in sample images - there was still frame-wide "coma" aligned with the CCD.
At first, I was making small adjustments to the height of the corners of the CCD - 0.2mm max. I decided to make gross movements instead, and didn't see any change in the test images. Aha! Something else is going on. It turned out to be "tearing" in the image introduced by software. The QHY8 is supported with a custom driver under Nebulosity on the Mac. Unfortunately, these seem to have some problems. After trying Nebulosity under Windows with the official QHY drivers, I finally got a very nice test image with a flat field. Nothing is perfect though, I have to reinstall the drivers frequently.
When playing around with the CCD alignment, I noticed that the cold finger the CCD is on is levered on one side. This is the side with one spacer on top of a component. I took out the screw I previously put on the right hand side, straightened the spacer and put it on the right hand side. When I reassembled the CCD, the CCD was pretty much perfectly aligned!
If the clouds of the past two months clear, hopefully I will get some imaging done with the QHY8.
So, I spent a bit of time fiddling with the QHY8 getting the CCD square to the front plate. I adjusted the rear screws and was able to get the CCD square according to my measurements. But no matter how I changed the tension, I couldn't see any difference in sample images - there was still frame-wide "coma" aligned with the CCD.
At first, I was making small adjustments to the height of the corners of the CCD - 0.2mm max. I decided to make gross movements instead, and didn't see any change in the test images. Aha! Something else is going on. It turned out to be "tearing" in the image introduced by software. The QHY8 is supported with a custom driver under Nebulosity on the Mac. Unfortunately, these seem to have some problems. After trying Nebulosity under Windows with the official QHY drivers, I finally got a very nice test image with a flat field. Nothing is perfect though, I have to reinstall the drivers frequently.
When playing around with the CCD alignment, I noticed that the cold finger the CCD is on is levered on one side. This is the side with one spacer on top of a component. I took out the screw I previously put on the right hand side, straightened the spacer and put it on the right hand side. When I reassembled the CCD, the CCD was pretty much perfectly aligned!
If the clouds of the past two months clear, hopefully I will get some imaging done with the QHY8.
Borg 77EDII
Note
I originally wrote this post back in November 2009, and it has languished as a draft. Since then, I've added the 135mm tube (7135) that allows use of the f/4 ED reducer and the new 0.78DGT triplet reducer (7878).
My new Borg 77EDII (available from Hutech outside of Japan) arrived today from Starbase.
The 77EDII package (6000 and 2178) comes with a drawtube, helical focusser, two M57 extension tubes (7509, 7508) that also allow use of 2" accessories, and a T-ring adapter (7522). The tube has a clever flat mount area that can be used to attach the scope to a tripod, or to attach a finder mount or other accessories.
Both the tube and the lens assembly come with caps for use when the scope is broken down for transport. Nice. I would've liked these for my 125SD - there is not even the option to buy them separately. The lens cell doesn't appear to be adjustable, but looks like it will accept 77mm filters (note it doesn't, you can use 82mm filters if you take the nameplate off, see here). The lens hood is retractable, but doesn't slide into place with a satisfying click, as the Pentax 75SDHF does, or have a screw to hold it in place, like the Tak Sky-90 and FSQ-85ED. However, the hood is small and light, so I don't think it being held in place by friction will be a problem.
In addition I bought the 80mm rings (7080), the plastic clamshell (5503) and a Vixen-style finder mount (7755n). I also added one accessory that currently seems to be available only in Japan, the Yuetsu-27g base ring from Scopelife. This is the well-machined (カワセミ or "Kingfisher") blue ring in the photos. This provides a tighter fit around the extensible draw tube and reduces sag. I became aware of this accessory through the Borg "topics" blog (Japanese). Note the blog is now at http://www.tomytec.co.jp/borg/world/blog/.
The flexibility and value for money of Borg scopes and accessories seems to increase the more you buy. I can use the M57 FeatherTouch focusser and MDX "helicoid" with ED F4DG reducer for my 125SD on the 77EDII with no problem. I think I can also use the 0.85x DG (7885) and 0.66x DGT (7866) reducers for the mini-Borg series that I have for use with my 60ED. Both of these reducers are usable up to 500mm focal length, only cover an APS-C sized sensor, but have the advantage of being tiny.
Compare this to my Taks. I have a 35mm reducer, (separate) 35mm flattener and 1.6x extender specific to the TOA-130/150, the 0.73 reducer ED and 1.5 extender ED for the FSQ-ED and Sky-90 reducer and Extender-Q for the Sky-90 and FSQ. To be fair, the extenders can all be used with other scopes - I think. And with some ingenuity some of the reducers can be used on other scopes, but not easily.
With the F4DG reducer, the focal length of the 77EDII is around 330mm at f/4.3. On a 35mm full frame this is just over 6 by 4 degrees, with a 7.5 degree diagonal. This should provide nice wide-field images. For H-alpha, the Olympus 250/2 and 250/2.8 have the advantage of speed, though at the cost of weight. The Pentax 645 300/4 provides a comparable FOV at a comparable weight, but the Borg's flexibility would have it win for a trip. Anyway, it will be fun to try them out and compare.
I missed out on the Borg 0.85x DGL reducer/ (7887) for 35mm full-frame, so will wait and pick up the 0.78x triplet reducer when it becomes available. I recently managed to find the fairly rare 35mm 1.04x flattener (7784) on Yahoo Auction in Japan, which I will pick up over the New Year holiday. This set of reducers/flatteners will give 330, 395 and 530mm focal lengths on a full 35mm frame. Surely in terms of flexibility, this has to be one of the best small portable photo-visual refractors available?
The 77EDII is pretty large compared to the 60ED when assembled.
I originally wrote this post back in November 2009, and it has languished as a draft. Since then, I've added the 135mm tube (7135) that allows use of the f/4 ED reducer and the new 0.78DGT triplet reducer (7878).
My new Borg 77EDII (available from Hutech outside of Japan) arrived today from Starbase.
The 77EDII package (6000 and 2178) comes with a drawtube, helical focusser, two M57 extension tubes (7509, 7508) that also allow use of 2" accessories, and a T-ring adapter (7522). The tube has a clever flat mount area that can be used to attach the scope to a tripod, or to attach a finder mount or other accessories.
Both the tube and the lens assembly come with caps for use when the scope is broken down for transport. Nice. I would've liked these for my 125SD - there is not even the option to buy them separately. The lens cell doesn't appear to be adjustable, but looks like it will accept 77mm filters (note it doesn't, you can use 82mm filters if you take the nameplate off, see here). The lens hood is retractable, but doesn't slide into place with a satisfying click, as the Pentax 75SDHF does, or have a screw to hold it in place, like the Tak Sky-90 and FSQ-85ED. However, the hood is small and light, so I don't think it being held in place by friction will be a problem.
In addition I bought the 80mm rings (7080), the plastic clamshell (5503) and a Vixen-style finder mount (7755n). I also added one accessory that currently seems to be available only in Japan, the Yuetsu-27g base ring from Scopelife. This is the well-machined (カワセミ or "Kingfisher") blue ring in the photos. This provides a tighter fit around the extensible draw tube and reduces sag. I became aware of this accessory through the Borg "topics" blog (Japanese). Note the blog is now at http://www.tomytec.co.jp/borg/world/blog/.
The flexibility and value for money of Borg scopes and accessories seems to increase the more you buy. I can use the M57 FeatherTouch focusser and MDX "helicoid" with ED F4DG reducer for my 125SD on the 77EDII with no problem. I think I can also use the 0.85x DG (7885) and 0.66x DGT (7866) reducers for the mini-Borg series that I have for use with my 60ED. Both of these reducers are usable up to 500mm focal length, only cover an APS-C sized sensor, but have the advantage of being tiny.
Compare this to my Taks. I have a 35mm reducer, (separate) 35mm flattener and 1.6x extender specific to the TOA-130/150, the 0.73 reducer ED and 1.5 extender ED for the FSQ-ED and Sky-90 reducer and Extender-Q for the Sky-90 and FSQ. To be fair, the extenders can all be used with other scopes - I think. And with some ingenuity some of the reducers can be used on other scopes, but not easily.
With the F4DG reducer, the focal length of the 77EDII is around 330mm at f/4.3. On a 35mm full frame this is just over 6 by 4 degrees, with a 7.5 degree diagonal. This should provide nice wide-field images. For H-alpha, the Olympus 250/2 and 250/2.8 have the advantage of speed, though at the cost of weight. The Pentax 645 300/4 provides a comparable FOV at a comparable weight, but the Borg's flexibility would have it win for a trip. Anyway, it will be fun to try them out and compare.
I missed out on the Borg 0.85x DGL reducer/ (7887) for 35mm full-frame, so will wait and pick up the 0.78x triplet reducer when it becomes available. I recently managed to find the fairly rare 35mm 1.04x flattener (7784) on Yahoo Auction in Japan, which I will pick up over the New Year holiday. This set of reducers/flatteners will give 330, 395 and 530mm focal lengths on a full 35mm frame. Surely in terms of flexibility, this has to be one of the best small portable photo-visual refractors available?
The 77EDII is pretty large compared to the 60ED when assembled.
Borg 2010X2 is a 71mm fluorite
The new Borg 71 FL is out. It can be used with the mini-Borg tubes/accessories as well as the 80mm diameter tubes. The first batch of 100 has nearly sold out already. I lasted all of two days without ordering one.
It's 400mm f/5.6. With the 0.66 DGT reducer, this will be 264mm @ f3.72, roughly 4.8 by 3.2 degrees on an APS-C sensor. With the 0.85 DG reducer, 340mm @ f/4.69, which is 3.7 by 2.5 degrees.
It's 400mm f/5.6. With the 0.66 DGT reducer, this will be 264mm @ f3.72, roughly 4.8 by 3.2 degrees on an APS-C sensor. With the 0.85 DG reducer, 340mm @ f/4.69, which is 3.7 by 2.5 degrees.
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