Star 71 Astrograph
- I just took delivery of the new Star 71 Astrograph, composite FOV image attached. I live near the beach, low clouds and fog have made testing difficult, but initial results exceed my expectations. The field is flat and fully illumated. Star tests are excellent, and the OTA is built like a tank.
- Looks really nice and I thought about trying one of these myself! Have you been able to check the image scale and confirm that it's actually f/4.9?I know there were some major discrepancies with both the GTF81 and GTF102 between their advertised f-ratios and what they actually delivered.Dan
I use a spread sheet to calculate field of view. Based on pixel size and chip size, I should get about 2 1/2 X 3 1/2 degrees, which the photo shows. I am not sure how to measure image scale?
- Can be done pretty easily - I use a freeware called CCDcalc. If you tell me the kind of camera you use, I can figure out the image scale and then expected FOV. 2.5X3.5 deg is pretty wide, so it might very well actually be f/4.9.Dan
- Dan - I use a Canon XSi DSLR it is 4272 X 2848 with 5.2 micron pixels. Thanks for your input, I will look into CCDcalc. I plan to give it a dark sky test on the 21st.
- I had the Star-71 in some dark sky last weekend, this is 30 minutes, 3X10minutes), of M101 and the area around it, If "The Sky" is correct, some of the galaxies noted are below magnitude 14. A Canon XSi was used for the image.
- I must've missed your reply. Sorry! If the Star 71 is really f/4.9, your total field of view with your Canon should amount to 146 X 220 arcminutes (rounded a bit). So about 2 1/3 degrees by 3 2/3 degrees - which is about what you got, right?Sounds like a really nice scope!