NGC 457, "ET" Cluster, coma corrector + focal reducer test (David Dearden)

Celestial hemisphere: Northern · Constellation: Cassiopeia (Cas) · Contains: 34 Cas · NGC 457 · Owl Cluster · The star φ Cas

NGC 457, "ET" Cluster, coma corrector + focal reducer test, David Dearden

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NGC 457, "ET" Cluster, coma corrector + focal reducer test

This is another focal reducer + coma corrector test, but this time I don't have the IR filter removed and things already look much better. Guiding south only, 60 s subframes, no chiller as it is already pretty cold tonight and the CCD is running at -0.5 °C with no chiller. I did a laser collimation first, then further collimated on a star with the focal reducer + coma corrector in place. This was at a coma corrector-imaging plane distance of 66 mm. Coma was still evident around the edges, but not as bad as with the greater spacings. I can’t go less than this without getting the proper adapters, but I have discovered that StarTools can take the coma out in software fairly well as long as you are careful with your star mask and don’t over-apply the correction. I’m sure it also helped that I had the IR filter in place!

Date: 13 Nov 2012

Subject: NGC 457 “ET” Cluster

Scope: AT8IN+High Point Scientific coma corrector+0.5x Antares telereducer

Filter: None

Mount: CG-5 (Synta motors)

Guiding: Orion ST80 + DSI Ic + PHD 1.13.7

Camera: DSI IIc (no chiller, but 0 °C)

Acquisition: Nebulosity 3.1.2, no dither

Exposure: 109/90 x 60 s

Stacking: Neb 3, bad pixel map & flats, bias included, normalize first, trans+rot align, 1.5 SD stack

Processing: Neb 3 crop, autocolor, saturation; StarTools Wipe (Vignetting), Develop, Deconvolute, Track, Repair (Draw in to Average), Life. CS6 Astronomy Tools star color enhance.

Original
Final
B

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Status	Basic success
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Astrometry.net job	6573031
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