Borg 77EDII Astrograph – Roddier Analysis

After 5+ years of imaging with Borg 77EDII reduced down to F/4.3 with the Super Reducer (part #7704) which really covers entire full-frame field (36x24mm) very nicely though with notable vignetting in the very corners I am still using this nice, compact and lightweight, feather touch equipped short focal length telescope for widefield imaging and for expeditions as it’s very easy to take it on board of an airplane (total weight is around 2.5kg).

In this short test I have focused on Roddier Analysis using WinRoddier 3.0 software that is now very easy to use especially with WRCALC utility that calculates the major parameter – how many pixels should the defocused star occupy on the chip of the camera used to capture data along with focus travel in order to reach such a defocus (either inward or outward from focused bright star in the middle of the FOV) valid for tested wavelength, see:

It is important to do the test for selected wavelength which is set in the preferences window of WinRoddier:

Don’t forget to adjust Strehl precision to 3 to see other value then 0 or 1 in the results window!

Also, for my testing, I have adjusted Preferences->Algorithmes->Nombre maximal d’iterations from 3 to 7. All other values were left unchanged (default).

Test Setup Parameters:

Test Results – Charts/Images:

Test Result in Numbers:

Comment:
It looks too much perfect to me (Strehl 0.989), but it’s true that in Green color the Borg really performs very, very well (as well as in Red and all narrowband, obviously) so next time I should test the Blue color too as Blue (and Luminance) is the „worst“ – has biggest FWHM of stars even in perfectly focused images.

To support my words on performance in Green, here’s a sample image (raw, unprocessed, Light frame) took on 1st of February 2014 on Tenerife at 2300m above sea level. The only drawback is that the JPG quality was set to 50% due to file size limits (1MB) on my blog.

References
Borg 77EDII Astrograph – an user “review”
Projet WinRoddier