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Critters, Field-of-View Measurements

Posted: 12 April 2013

The observatory was opened on Thursday, 11 April 2013, at 1815 MST, 75°F. The sky was mostly cloudy, but there were some holes. I decided I could do field-of-view (FOV) measurements using a newly received star diagonal and a new eyepiece. I will post a full review of the diagonal and eyepiece soon.

As I was opening the observatory door, this neighbor came to see me:


Another neighbor monitored my activities from the top of a POD bay:


Beginning at 1830 MST, about 20 minutes before sunset, I slewed the 8" LX200-ACF telescope to Sirius, which was visible through some thin clouds. It remained visible most of the time I was doing FOV measurements of all of my eyepieces and the D7000 DSLR camera. To determine the actual true field-of-view I would move Sirius to the north or south edge of the eyepiece/camera view and record the Declination as displayed on the AutoStar MODE screen. I then slewed to the oppposite south/north edge and recorded that Declination value. I have an Excel spreadsheet that does the calculations using these DEC values and presents the results in a nice table.

An older version of the table is available online for those who want to use it for their own accessories. In the FOV tab, unhide the rows below each section to enter DEC values. Hide the rows to print the table for use at the telescope. Click to get the FOV/Magnification Table.

I completed all the FOV measurements at 2106 MST. Due to the extensive cloud cover I did no visual tests this night. That will have to wait for clear skies.

The observatory was closed at 2140 MST, 57°F.

Comments are welcome; use the Comments section below, or you can Email Me. Thanks.

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