May 12, 2018
Well, look what arrived in the mail! Yes, that's a William Optics ZenithStar 61, a very portable apochromatic refractor from my favorite telescope maker. This cool little scope is like a baby version of my GT81, with a synthetic fluorite objective lens (which has some of the best lens properties, including ultra-low dispersion of light, etc.) I will write up a review after a few nights out with the ZS61. I can't wait for clear skies!
A few shots of the astronomy workbench, where I'm testing out the ZS61 with a guidescope, focuser, and the ZWO ASI071C camera.
May 5, 2018
I ordered the William Optics Zenithstar 61 APO today. This is a very small f/5.9 360mm focal length refractor, and I'm going to be using it as an ultra-portable scope, mostly for wide field targets like NGC7000 North American Nebula, M42, M31, Cygnus Loop, and other massive deep sky objects. I didn't order the Flat-61 field flattener because I want to see how well the WO Flat6A 0.8x Field Flattener/Reducer works with the ZS61. The Flat6A will bring this scope to f/4.7 288 focal length, which is great--I normally work at this f ratio with the GT81.
William Optics ZS61 APO - Field of View Info
Atik414EXCCD - f/5.9 Res: 3.69"x3.69" FoV: 1.43° x 1.07° (85.8 x 64.2)
ZWO ASI071MC - f/5.9 Res: 2.74"x2.74" FoV: 3.76° x 2.5° (225.6 x 150)
QHY 5iii178C - f/5.9 Res: 1.37"x1.37" FoV: 1.18° x 0.79° (70.8 x 47.4)
WO 0.8x Reducer/Flattener
Atik414EXCCD - f/4.72 Res: 4.61"x4.61" FoV: 1.78° x 1.33° (106.8 x 79.8)
ZWO ASI071MC - f/4.72 Res: 3.42"x3.42" FoV: 4.7° x 3.12° (282 x 187.2)
QHY 5iii178C - f/4.72 Res: 1.72"x1.72" FoV: 1.48° x 0.99° (88.8 x 59.4)
March 29, 2018 - ZWO ASI071MC-Color Camera Review
The ZWO ASI071MC-C camera is a new purchase for me. I'm coming from a couple years of narrowband imaging with an Atik 414EX mono CCD, and I was specifically looking for a cooled color camera. There are a lot of great OSC cameras out there, and I put some time into researching Atik, QHY, and ZWO. First off, if the ASI071 is in your potential buying list for gear, you probably know ZWO has improved the design around dew control with the next-generation ASI071 Pro, along with a couple other nice-to-haves like 256MB DDR3 buffering. So far, with a few astro sessions using the ASI071 I haven't experienced anything that makes me regret buying the original (lower-cost) version.
A couple things to be aware of: 1) I went out of my way to look for the issue (reported on Cloudy Nights and elsewhere) with dew freezing on the AR window, and if you’re just starting out for the night and push the temp below -10 or -20C you may see this, but as soon as you start taking subs that evaporates--literally. Simply put: there’s moisture in the air and you’re chilling this device down well below zero, under the right conditions you will see condensation freezing on the glass, with that distinctive pattern showing up in an exposure or two. ZWO has corrected this in the Pro by preheating the window, but if you come across it, you can accomplish the same thing by taking a few 30 second test exposures. Basically, once you start using the camera this issue goes away. 2) The Pro version uses faster memory for more efficient transfer speeds and buffering. That’s great--faster is pretty much always better, but even so, I am impressed with the download speeds from the ASI071MC-C, given that a single 16-bit FITS file from this camera is 32MB. With my last couple astro imaging sessions I’ve used an old Intel Celeron-based laptop running Ubuntu MATE and Ekos/KStars/INDI. Not the fastest setup around but more than adequate for the file sizes and transfer speeds. I haven’t tried this camera out with Ekos/KStars/INDI running on one of my Raspberry Pi boxes, or with SGP on Windows 10, but soon!
For my criteria, budget, and style of astrophotography the ASI071MC-C seems to have it all. The main features that tipped the balance are: very competitive price, 2-stage TEC, low read noise, 14-bit ADC, APS-C sized 16MP sensor, 4.8 μm pixels, and full well capacity of 46ke (You can really play with gain and offset, and still have enough capacity for capturing those soft nebulous gradients). Of course I was also impressed by some of the shots others have taken with the camera--take a look on Astrobin. One final thing: the built-in USB hub. I thought this was an interesting idea, but didn’t know how useful it would be until I started using the camera. Now, it bothers me that other cameras (I have Atik, QHY, and other ZWO cameras) don’t have a couple extra USB ports. These really came in handy for my guide cam and focuser.
March 11, 2018
Setting up the William Optics GT81 tonight with my new ZWO ASI071MC camera. I'm also trying out--again--the 30mm apt/135mm fl guide scope with the ZWO ASI120MM-S, this time with the camera threaded directly to the scope, reducing the backfocus a few more millimeters. This will be my first time out with the new main camera, and I've been anxious to see what it can do for almost a week. The ASI071MC is a color CMOS camera with an impressive dynamic range, TEC cooling, 16MP APS-C sized Sony sensor with 4.8μ pixels. The idea is to have the new color camera compliment the Atik 414EX monochrome CCD I normally use. The Atik with the Nikon 180mm f/2.8 lens has almost the same field of view as the ASI071MC with the William Optics GT81. (The Atik + Pentax Takumar 200mm f/4 is even better). You can't tell with the way I've configured the top dovetail rail and guidescope, but the plan is to be able to run both cameras simultaneously with similar FOV, one color, the other with narrowband filters, in some ways doubling my productivity.
Resolution & FOV
William Optics GT81 f/5.9 + ZWO ASI071MC-C
Res: 2.06"x2.06"/pixel FOV: 2.83° x 1.88° (169.8' x 112.8') Dawes Limit: 1.43 arc/secs
William Optics GT81 f/4.7 + 0.8x Reducer/Flattener + ZWO ASI071MC-C
Res: 2.58"x2.58"/pixel FOV: 3.54° x 2.35° (212.4' x 141.0') Dawes Limit: 1.43 arc/secs
Gain & Offset
• Max Dynamic Range: 0 Gain, 8 Offset
• Unity Gain: 90 Gain, 20 Offset
• Min Read Noise: 240 Gain, 65 Offset
February 27, 2018
Setting up the William Optics GT81 tonight, with the Atik414Ex Mono CCD. There's a big bright moon out there tonight, so I'm not sure what I'm going to shoot. I'm mostly testing out a few things. First, a 2" UHC/LPR filter I've had for a few years--and I don't think I've used it for almost that long. The other is my smaller, short focal length guide scope--135mm FL (that black tube on the other side of the main refractor).
January 10, 2018
This is my "astro cart", which allows me to get everything connected, bolted on, balanced, and ready to go while still in the house--before I go out in the freezing temps. I can roll it right up to the back door that leads out to the deck. One of the real advantages of the iOptron CEM25P is its light weight to carrying capacity specs. The lower total weight allows me to pick up this whole setup (OTA, camera, counter-weights and all) and carry it to the pier. (That's my William Optics GT-81 APO next to the AstroTech, right side of the cart).
Getting ready for some potential clear skies tomorrow or the next day, and I'm doing the prep setup with the Atik414EX on the AstroTech RC scope--f/7.2 with the focal reducer/field flattener. I have some smaller targets picked out, and might even go back for more of the Horsehead nebula (with the RC's longer focal length), as well as other interesting stuff in Orion.
Note on the iOptron CEM25P: The mount only weighs 10.4 lbs (4.7 kg), but has a payload capacity of 27 lbs (12.3 kg) without the counterweights. Total weight of the William Optics refractor, imaging train (Atik CCD, filter wheel, filters, and extensions), guide scope and camera, and various other gear ends up around 15 lbs (6.8 kg), and with the AstroTech it's another 5 lbs, so still well under the 27. That's where you're going to get the best guiding and alignment results--not pushing that capacity boundary. (Just for comparison, my Orion Atlas EQ-G mount weighs 54 lbs (24.5 kg) just by itself, and has a payload capacity of 40 lbs(18 kg)--so yeah, it can carry more, but there's no way I can handle setting up except when everything is in pieces).
My Refractor Setup as of October 5, 2017
December 25, 2017
My Winter Astro Setup, essentially the same William Optics GT-81 - iOptron CEM25 combo, with the addition of the iOptron Tri-Pier Adapter, some 6x8 aluminum plates off eBay, and one treated 4x4 post from Home Depot.
The good side of winter and astrophotography is it’s usually dry on clear nights--and “clear” really means clear in terms of astronomical seeing, atmospheric turbulence and all that. Downside is that it’s freakin’ cold. Tonight it’s supposed to get down to about -8°C (about 20°F), pretty cold to be out for a long time, but not painfully cold.
Here are a couple shots of my setup for tonight--and possibly the rest of the winter. (William Optics GT-81, CEM25P EQ mount, Atik414Ex mono CCD, WO 50mm guidescope with ZWO ASI120S-MM guide cam, INDI/KStars/Ekos observatory control). What’s cool is that I can unbolt the mount with the pier adapter and aluminum base plate (they’re all bolted together) from the 4x4 post and top plate, and carry in the entire setup--mount, scope, cameras, etc. What I especially like about this is the ease with which I can setup and tear down each night. The whole thing remains balanced and ready to go, with polar alignment reduced to very fine adjustment to zero in on the NCP.
Note on my other mount: I probably won’t use my Orion Atlas EQ-G mount until spring when things start to warm up, and that’s based on the weight of the Atlas and the low temperatures--with ice adding some difficulty to the setup process. (Yeah, I don’t want to lug around this monster with any probability of slipping, landing on my back, and having to catch fifty or sixty pounds of metal out of the air before it kills someone). The average winter low in New Hampshire is around -12°C, and the average winter high temp is still below 0°C (around 30°F). It’s not unusual for things to get down to -20 to -30°C (-10 to -20°F). We’re still in December, so early in the season, but we’re already getting repeated snow storms interspersed with temps above 0°C (32°F). We typically get a few days of warmer weather here and there, snow and ice melting weather, but there haven’t been enough of them to make a dent in the accumulating snow and ice we have in the yard, driveway, or back deck. We just ended yesterday (the 25th) with another 6 inches or so. When there’s ice, lighter is better.
Beyond the meridian test
I love the iOptron CEM25P mount. It's center-balanced, lightweight, very accurate if you don't push the 27lb limit, and easy to work with under almost any app that uses ASCOM or INDI. I regularly shoot 5 - 10 minute guided subs without issue, even 20 minute subs, depending on the target. Besides capacity, the one difference that stands out from my Orion Atlas EQ-G is how far the CEM25 can take things beyond the meridian. This is a quick shot--yes, I know it's not directly centered, but it does give a rough post-meridian estimate of 20° or so. That's enough when you're chasing M42 with those last ten minutes of exposures. I do think the Atlas has more room here though, but I'll have to test that. (This is my wide-field setup--Nikon lens, QHY primary cam, ZWO guide cam)
# This is a config file for the Astrometry.net 'astrometry-engine' # program - it contains information about where indices are stored, # and "site policy" items. # Check the indices in parallel? # # -if the indices you are using take less than 2 GB of space, and you have at least # as much physical memory as indices, then you want this enabled. # # -if you are using a 64-bit machine and you have enough physical memory to contain # the indices you are using, then you want this enabled. # # -otherwise, leave it commented-out. #inparallel # If no scale estimate is given, use these limits on field width. # minwidth 0.1 # maxwidth 180 # If no depths are given, use these: #depths 10 20 30 40 50 60 70 80 90 100 # Maximum CPU time to spend on a field, in seconds: # default is 600 (ten minutes), which is probably way overkill. cpulimit 300 # In which directories should we search for indices? add_path /usr/share/astrometry # Load any indices found in the directories listed above. autoindex ## Or... explicitly list the indices to load. #index index-219 #index index-218 #index index-217 #index index-216 #index index-215 #index index-214 #index index-213 #index index-212 #index index-211 #index index-210 #index index-209 #index index-208 #index index-207 #index index-206 #index index-205 #index index-204-00 #index index-204-01 #index index-204-02 #index index-204-03 #index index-204-04 #index index-204-05 #index index-204-06 #index index-204-07 #index index-204-08 #index index-204-09 #index index-204-10 #index index-204-11 #index index-203-00 #index index-203-01 #index index-203-02 #index index-203-03 #index index-203-04 #index index-203-05 #index index-203-06 #index index-203-07 #index index-203-08 #index index-203-09 #index index-203-10 #index index-203-11 #index index-202-00 #index index-202-01 #index index-202-02 #index index-202-03 #index index-202-04 #index index-202-05 #index index-202-06 #index index-202-07 #index index-202-08 #index index-202-09 #index index-202-10 #index index-202-11 #index index-201-00 #index index-201-01 #index index-201-02 #index index-201-03 #index index-201-04 #index index-201-05 #index index-201-06 #index index-201-07 #index index-201-08 #index index-201-09 #index index-201-10 #index index-201-11 #index index-200-00 #index index-200-01 #index index-200-02 #index index-200-03 #index index-200-04 #index index-200-05 #index index-200-06 #index index-200-07 #index index-200-08 #index index-200-09 #index index-200-10 #index index-200-11