Tonight I'm testing out the ZWO ASI071 and the AstroTech RC6, with an Off-Axis Guider (QHY5iii178 guide camera binned 2x2). I've never tried this mix together, so we'll see how it goes. At 1350mm focal length this setup has a 0.73/pixel resolution. So, yeah, it's going to be oversampled. And there's also a big old gibbous moon out tonight, and the weather is not planning to cooperate. My hopes are fairly low.
Going to run some manual focus tests on my wide-field narrowband setup, if I can see the stars tonight. I just want to see if I have the backfocus correct for the Nikon f/2.8 180mm lens. I'm using a 2" Optolong 7nm Ha filter with the Atik 414EX mono CCD camera. No guiding with this tonight, but normally I would have the 130mm guide-scope and ZWOASI120MM-S on top of the aluminum camera/lens ring (ZWO 78mm Holder Ring for ASI Cooled Cameras). My hydrogen-alpha filter is in the AstroShop 2" Filter Drawer System with the tripod foot, which just adds more stability to this setup. You may also notice--if you're familiar with the iOptron CEM25P--that I'm using the short counterweight bar with a single weight. I can carry this whole rig around without taking anything apart.
Yesterday I set up for a couple broadband color targets, and went with the Astro-Tech 6" f/9 Ritchey–Chrétien with 1350mm focal length. I paired the RC with the ZWO ASI071MC cooled color camera. And this is the first time I'll be using the DeepSkyDad Autofocuser AF1, which fits perfectly on the stock Crayford focuser--although you can't see it in this shot because I have the focus knobs vertical on the right site of the scope. Not using an OAG with this setup, but going with the William Optics 200mm guide scope and ZWO ASI120MM-S mono camera.
NGC 7023, Iris Nebula is a beautiful reflection nebula in Cepheus, about 1,300 lightyears away.
I ran into a funny situation with my off-axis guider and one particular filter, an Optolong 685nm longpass filter. The filter itself gave me some amazing shots of star clusters and even did well with IR emissions from nebulae and galaxies. I run a set of mid-range Astronomik narrowband filters in the ZWO EFW I have attached to the ZWO ASI1600MM-Pro mono camera, and within reason, they’re parfocal. In SGP I’m running the autofocus process every filter change anyway, but I don’t see much difference. The IR filter glass on the other hand is thick enough to move the focus far enough to affect the focus of the guide camera in my OAG. I had to go out to the scope and adjust the guide focus in PHD2.
One solution is to go with the guide scope when using the IR filter, but I don’t know if PHD2 can support this automatically, or if I have to stop, disconnect the OAG camera when switching to IR, and connect the camera on the guide scope. It will be an interesting workflow. I’m wondering if ASCOM/SGP can work with three connected ASI cameras? ASCOM’s approach seems to be to add a number after the device name, like ASI Camera , ASI Camera . Will there be an ASI Camera ?
Although this sounds like a fun experiment, I’m going to stick with my OAG, and swap out the near IR filter at some point--maybe for a tighter Ha filter, a 3nm? Up to now I’ve never paid attention to the thickness of the glass for filters, but I’m going to look into that now.
Image: I got one frame into the IR sequence and PHD2 wasn’t happy:
I'm back on Windows to play around with Sequence Generator Pro (http://mainsequencesoftware.com/) and NINA (https://nighttime-imaging.eu/) NINA stands for Nighttime Imagine 'n Astronomy. I used SGP almost exclusively before moving to Ekos/KStars about two years ago. It's one of the most powerful astro apps on Windows, and I've always recommended it. I'm also going to be trying out the latest version of NINA, which just looks amazing. I can't wait to see where this app goes.
Equipment Setup Notes
ZWO ASI 1600MM-Pro
William Optics GT81 + WO 0.8x Reducer
Sensor: 3.8µ pixels, 4656 x 3520
ZWO ASI071MC + Nikon 180mm f/2.8
Sensor: 4.78µ pixels, 4944 x 3284
ZWO ASI017MC + AstroTech AT6RC
Sensor: 4.78µ pixels, 4944 x 3284
Nikon D750 + AstroTech AT6RC
Sensor: 5.98µ pixels, 6016 x 4016
QHY5III178 + 50mm 1.4 lens
Sensor: 2.4µ pixels, 3096 x 2080
In the field--well, not really, but I was a little under a 100 miles away in western Massachusetts testing out the portable narrowband setup with my William Optics GT81 APO refractor, Moonlite automated focuser, ZWO ASI1600MM-Pro Mono camera, iOptron CEM25P mount. It snowed and was cloudy the rest of the time, but I did have a chance to really test out the setup away from the house, and it all worked beautifully. Unfortunately I also forgot to take my Macbook Pro, but ended up running everything from my iPhone using Jump Desktop to remote into the astro system. The weather didn't cooperate, but so what? We had such a fun time down at Lisa and Neil's place this weekend, and just to prove there was at least a little astronomy stuff going on, here's a pic of my setup running in the library.
Tonight's setup: William Optics GT81, Moonlite Focuser, ZWO ASI1600MM-Pro, ASI 120MM. This is my narrowband setup, and tonight it's all about the focuser.
Our beautiful planet rotates on its axis once every 23.93447 hours (23 hours, 56 minutes, 4.091 seconds). This is one sidereal day--sidereal time is based on the earth's rate of rotation measured relative to the stars that are--for the most part--fixed in position. Here we go: 23.93447 hours = 86164.091 seconds. So, we need to do a 360 degree rotation of the right ascension motor shaft in 86164.091 seconds to match the earth's rotation speed. Sounds simple enough. Backing into the time/revolution (360 deg) before the 100:1 gearhead ratio, we have: 86164.091 / 100 = 861.64091 seconds, or 14.3606 minutes / 360 degrees, which is close to what I'm getting for a full rotation with my current test system: NEMA 11 stepper + 100:1 planetary gearhead and A4988 stepper driver running with 1/16 microstepping. I'm probably going to build the second prototype with a NEMA 17 + 139:1 planetary gearhead, but still waiting on that to arrive. And I will most likely continue to run with 1/16 microsteps. The downside is microstepping significantly reduces torque--I'm sacrificing torque for slower, smoother steps, but I'm thinking I will make up some of this with the 100:1 harmonic drive gearhead (CSF-14-100-GH-F0ACB). The idea is to get the motor with the planetary gearbox to do one rotation in a little over 14 minutes, and then by adding the harmonic drive I'll multiply the rotation time by 100, and we should end up around 86164.091 seconds, or one sidereal day. I think that sounds right? (Also, don't forget the direction is reversed with the harmonic drive--clockwise rotation of the wave generator results in the flexspline moving counterclockwise).
The shot below has my attached 3D printed adapter for a camera mount. Once I test the rotation speed adequately, I will try out some long exposures with the Nikon.
Here's the latest component and wiring setup, driven by an Arduino Nano and A4988 Stepper Driver, with the whole thing running off a single 12vdc power supply. The bottom frame is the entire rotation test taped together and functional.