First Light: Sky-Watcher Esprit 150mm

The following are accounts of Grand Mesa Observatory's first light imaging run using the Sky-Watcher Esprit 150mm ED F7.0 Triplet APO Refractor. This is the latest project of observatory director Terry Hancock, and all images were captured from the Grand Mesa Observatory in Western Colorado. The target chosen for first light was NGC 7635, which was chosen for its spectacular detail in both narrowband and broadband spectra. The telescope itself was sent to us by Sky-Watcher USA for testing, so hopefully these accounts will help answer any lingering questions some of you may have.

Thoughts from the Director:
"I acquired the data in Color using LRGB Filters and I added H-Alpha to the red channel and as a luminance layer. For the Hubble Palette image these were captured using Chroma 5nm filters, Ha was binned 1x1, OIII and SII binned 2x2. I’m very impressed with the Sky-Watcher 150 Esprit, using the big chip QHY16200A CCD Monochome camera with an OAG the Esprit 150 gives a very sharp image and a nice flat field, (Sky-Watcher quote a 43mm image circle), although a little slower than the TAK130, image quality is superb and unlike many APO refractors I have owned or tested the Esprit has a dedicated Field Flattener/corrector. For Autofocusing we purchased the Starizona Micro-Touch stepper motor which slips onto the dual speed side of the focuser, I’m using TheSkyX @ focus 3 for autofocus and it works great."

Total Integration time for HaLRGB = 8.25 hours
Total Integration time for Hubble Palette = 9.25 hours

Higher resolution images:
HST https://www.flickr.com/…/terryha…/44028733691/in/dateposted/
HaLRGB https://www.flickr.com/…/terryha…/43980066972/in/dateposted/

Image capture details:
Terry Hancock downunderobservatory.com
Location: GrandMesaObservatory.com Purdy Mesa, Colorado

LRGB Image:
Dates: August 3rd 2018
LRGB, 240 min, 6 x 600 sec each, bin 1x1
H-Alpha 255 min, 17 x 900 sec, bin 1x1
Camera: QHY16200A
Gain 0, Offset 130, Calibrated with flat, Dark & Bias
Optics: Sky-Watcher Esprit 150mm ED Triplet APO Refractor
Filters by Chroma (Narrowband are 5nm)
Image Acquisition software Maxim DL5
Pre Processed in Pixinsight
Post Processed in Photoshop

Hubble Palette Image:
Dates: July 7, 24, 26, 2018
H-Alpha 255 min, 17 x 900 sec, bin 1x1
OIII 150 min, 15 x 600 sec, bin 2x2
SII 150 min, 15 x 600 sec, bin 2x2
Camera: QHY16200A
Gain 0, Offset 130, Calibrated with flat, Dark & Bias
Optics: Sky-Watcher Esprit 150mm ED Triplet APO Refractor
Filters by Chroma (Narrowband are 5nm) 
Image Acquisition software Maxim DL5
Pre Processed in Pixinsight
Post Processed in Photoshop

The Bubble Nebula (NGC 7635):
NGC 7635, also called the Bubble Nebula, Sharpless 162, or Caldwell 11, is a H II region emission nebula in the constellation Cassiopeia. It lies close to the direction of the open cluster Messier 52 which can be seen in this image upper left. The "bubble" is created by the stellar wind from a massive hot, 8 magnitude young central star. The nebula is near a giant molecular cloud which contains the expansion of the bubble nebula while itself being excited by the hot central star, causing it to glow. It was discovered in 1787 by William Herschel

Product Review - QHY 168M

This is a prototype version of the the very popular QHY168C, except this one has been factory debayered by QHY to produce a fully monochromatic camera. The camera is mounted on a 12" solid tube Ritchey-Chretien telescope made by AstroTech, which has itself been fitted with the Optec Gemini Rotating Focuser. The filter wheel is a QHYCFW2-M with a 7 position 36mm Carousel. We gave just received and fitted a new set of Optolong Narrowband Filters which have blackened edges that are meant to reduce the halo problems.

High Performance
The QHY168C uses an APS-C format, 16 Megapixel, 14-bit CMOS sensor, the Sony IMX071. This sensor is also used in the Nikon D5100 camera. It has 3.2e- read noise at lowest gain and 2.3e- read noise at unity gain (system gain = 1e/ADU). The QHY168C also has a nice dynamic range close to 14 stops.

True RAW Image Output
While the QHY168C has the same CMOS sensor as the D5100, unlike the consumer camera the QHY168C offers True RAW Image output. In the DSLR implementation there is a RAW image output, but typically it is not completely RAW. Some evidence of noise reduction and hot pixel removal is still visible on close inspection. However, the QHY168C offers TRUE RAW IMAGE OUTPUT and produces an image comprised of the original signal only, thereby maintaining the maximum flexibility for post-acquisition astronomical image processing programs.

Unique Thermal Noise Reduction Technology
In addition to efficient 2-stage thermoelectric cooling, QHYCCD employs a unique thermal noise control technology to reduce CMOS sensor noise to a very low value without affecting the integrity of the raw image. This proprietary technology can be found to improve noise performance across the whole 165/168/247/367 product line, producing much better noise reduction than any competing camera model.

Zero Amplifier Glow
QHY168C has zero amplifier glow no matter how long the exposure time.

Anti-Dew Technology
QHYCCD has more than 10 years of experience designing cooled cameras. The QHY168C receives the benefit of that decade of design work by featuring full anti-dew technology for both CCD sensor cover glass and the sensor chamber optical window. The QHY168C has an electric heating board for the chamber window to prevent the formation of dew and the sensor itself is kept dry with our silicon gel tube socket design for control of humidity within the sensor chamber.

AR+AR Optical Window
In order to avoid halos around bright stars the QHY168C has a AR+AR coated optical window rather than the common IR cut window for Single-Shot Color cameras. This permits full access to the red wavelength of H-alpha and SII without attenuation by the window coating. For RGB color balance, without passing the near IR wavelengths above 700nm, a separate removable 2-inch UV/IR filter with the desirable passband characteristics is placed in a custom filter holder in front of the camera.