Linslaw Point, Walton OR, June 23-26, 2022

And now for something completely different.

While astronomers suffer from many ailments, including aperture envy, scope speed syndrome and focal length fever, for astrophotographers it is even worse.  First there is mount mania (I upgraded to a Losmandy G11 in 2021).  Then there is camera and filter upgrade compulsion.  And there is obsessive auto guiding performance disorder.  Most astronomers upgrade to larger and longer focal length telescopes.  I went in the opposite direction and purchased a Stellarvue SVX102T triplet apochromatic refractor.  This now allows me to photograph wide field deep sky objects and star fields.

This project was the first using the SV102T refractor with a 0.74x focal reducer, providing A 2.55-degree field width.  I purchased a new ZWO filter wheel and the large off-axis guider.  These components allowed for everything in the imaging train to be screwed together and threaded to the 0.74x focal reducer with an M48 fitting.  This image is the “first light” test taken in Cepheus as it was high in the sky all night.  Guiding with the OAG-L performed very well, with a total error ranging between 0.37 and 0.7 arcsec, even in moderate winds and average seeing conditions.  The results are decent, but there are a few flaws t be addressed.  First, in two of the corners, the stars are elongated.  While the back focus spacing is mechanically 55mm, with an additional 0.67mm for the 2mm filter thickness, the elongated stars may be due to tilt or optical aberrations in the focal reducer.  Second, the bright stars have halos.  This may be due to the quality of the ZWO filters.  An OTA at f/5.2 was also a new experience, so exposure times may not be optimal.  Next, while StarXTerminator did a good job at removing the stars, star image processing and stretching was not perfect.  The halos appeared as I stretched to get more small stars to become visible to reflect the rich star field in the field of view.  Finally, there are a few color artifacts that could be caused by the optical train or in the background extraction process using PixInsight.

LBN 552 and LDN 1228 are clouds of dust and gas in a much larger dark nebulae complex in Cepheus.  LBN 552 (Lynds Bright Nebula catalog) is supposed to be a bright nebula.  There is one star illuminating a small portion of the dust cloud.  A portion of LDN 1228 is on the right side of the image.  This is RNO 129, an arrow-shaped orange reflection nebula.  Cepheus is brimming with large clouds of dust and gas worth photographing.

Imaging details:

Stellarvue SVX102T refractor with 0.74x focal reducer (FL = 528mm, f/5.2)
ZWO large off-axis guider with a ZWO ASI 174MM mini guide camera
Losmandy G11 mount with Gemini 2
ZWO ASI 2600MM Pro cooled monochrome camera (-10oC)
ZWO 36mm Luminance, Red, Green, and Blue filters
Equatorial camera rotation: 90o

Software:    Sequence Generator Pro, ASTAP plate solving, PHD2 guiding, 
    Losmandy Gemini ASCOM mount control and web client interface,
    SharpCap Pro for polar alignment with the Polemaster camera,
    PixInsight 1.8.9 with StarXTerminator (AI version 10) and StarNet2,
    Photoshop CC 2022

Luminance  1.5 min x 180 subframes (270 min), Gain 100, Offset 68, 1x1 binning
Red             4 min x 24 subframes (96 min), Gain 100, Offset 68, 1x1 binning
Green          4 min x 23 subframes (88 min), Gain 100, Offset 68, 1x1 binning
Blue            4 min x 23 subframes (88 min), Gain 100, Offset 68, 1x1 binning