Introducing the William Optics RedCat 51, f/4.9 Petzval Refracting Telescope. First light with this wide-field high-quality imaging telescope that I take through its paces.
Over the last two weeks, I’ve had 3 imaging nights. KStars & EKOS 3.0 were released which fixed a ton of long standing issues with the scheduler. In addition to that nice software update, I got a Celestron CGX for Christmas! So, those two things combined and I set my sights on the only northern region available to me from the back yard and imaged IC417 on my AT6RC, and IC410 on my Explore Scientific 102mm FCD100 scope.
Here’s a recent photo of the setup.
So far it’s worked great. Average RMS has been between .6 and .8. My AVX was hovering between .8 and 2.0 RMS. I think I can get the CGX tuned a little more in guiding to get those numbers even lower, but have not attempted any adjustments. These are the numbers I’ve been getting without changing any of the default guide settings.
Here’s my setup at 5:30 am this morning. Taking good flats is key. I had been using the dawn sky to shoot flats for some time. EKOS has a feature where it will shoot flats of any desired ADU value. I’ve found that a median ADU value of 22,000 is perfect for my setup. I found this value through trial and error, by taking flats ad different ADU values, then calibrating with them to see what the results were. Anything above 24,000 overcorrected, and anything less than 20,000 under corrected, so I’m right in the middle now.
I recently discovered this really awesome and inexpensive light source for flats. It’s worked like a charm.
A3 Light Box by AGPtek - currently $47.99
First off, A3 is large enough to cover the front of most large scopes. It’s 11.69” x 16.53” and it’s a flat evenly lit LED panel with three built in brightness settings. It can be powered by the A/C plug it comes with, or through USB plugged into your laptop.
In the photo above I have it plugged into the laptop, and am taking my flats through EKOS. This makes capturing flats quick and easy.
Within EKOS, I build a camera sequence for all my filters, 50 images each, auto exposure set to ADU value 22,000. Then I run the sequence. Within seconds it measures the light from the frame, and knocks out 50, then switches filters, measures the light again, and bangs out another 50 frames. In about 2-5 minutes I can capture all my flats in one go.
Below are the two sequences I captured for the evening (Double Cluster, and M33). While short at under 2 hours each, you can see that they are clean and well calibrated thanks to the easy flats system I’ve been using.
Make no mistake, this is a BIG, little grab-and-go. The biggest I could fit on the iOptron Cube Pro mount. The AT60ED wasn't cutting it for planetary views. The mount has a weight limit of 8lbs, so I opted for the largest scope with the longest focal length that I could get to fit on this class of mount. That happened to be Celestron's C5 Spotting Scope. Yes, Celestron sells this as a spotting scope, but at it's heart, it's really a 5" Schmidt Cassegrain telescope with XLT Starbright anti-reflective coatings. It's focal length is 1250 at a speed of F10. It's perfect for planet and moon viewing. It's got almost 3 times the focal length of the AT60ED and it's only 6lbs. Two pounds under the weight limit of the mount. This gives me room to add a few light accessories. It pairs well with eye pieces from 32mm down to about 6mm.
HUBBLE AT HOME
A recent addition to my set of telescopes. This is probably the most economically viable Ritchey-Chrétien telescope money can buy. It can be found for around $350 at most places. I bought this one used for even less. The Ritchey-Chrétien design is probably most famous for being the same optical design that's in the Hubble Telescope. This is probably the largest scope I can feasibly put on my mount for weight reasons. The AVX has a 30lb max payload capacity, and the AT6RC is around 13lbs with no other gear. So, I'm probably pushing 18-20lbs of astronomical gear with this scope. Due to the long focal length, getting the polar alignment dialed in is crucial. But once set, I'm able to get some half way decent images out of it.
These images show all the gear set up and ready for a night of imaging. Pictured here is the AVX mount, AT6RC, Orion 60mm Guide scope, ZWO ASI1600MM-Cool camera for primary imaging, ZWO ASI224MC camera for guiding, the ZWO 8 slot electronic filter wheel with LRGB and Narrowband filters, an Astrozap dew heater on the guide scope, Astrozap dew shield, and a Bahtinov mask from Grosky.
This simple guide helps you polar align your Celestron equatorial mount when you have no view of the north star.
Some things that will be helpful for this tutorial:
Steps to align:
- The first thing you’ll need to do is set up your mount on level ground facing roughly north. Make sure you use a bubble level to ensure your mount is on a flat plane so that when it’s rotating around it’s azimuth the mount is not moving up and down slightly.
- It’s important you’re facing north within a few degrees, you can achieve this by using your phone’s compass feature (or Astro Locator) and laying it across the main telescope tube on a flat surface. You’ll want the phones settings set to face true north. This is already established in Astro Locator.
- Turn on your mount, and plug in your home site settings or let your GPS system update your time and location in the mount’s hand controller. I currently use a GPS, but prior to that I would watch the clock in Astro Locator, and set the time setting down to the second for accuracy.
- Use your mount’s hand controller to select 2-star alignment. It’s going to show you the name of a suggested star in the western hemisphere that it thinks is visible in your location. Since your mount is pointed roughly north, west is going to be anything directly to the left of your mount, and east will be anything directly right of your mount. The star it suggests might not be visible to you depending on your location and any objects that might be in the way (like houses or trees). This is where Sky Safari comes in handy. I open it up on the iPhone, zoom out so that I can see a fairly large portion of the sky, and press compass (one of the buttons on the bottom of the app). This allows you to pan your phone around the sky, and look for stars that you can actually see. Typically, the named stars in Sky Safari, are only the brightest stars, and you should now be able to visually identify stars in your night sky. Look for a bright star to the left of your mount, and correlate it to a named star in Sky Safari. Once you have a star picked out, use the up and down arrows on your telescope’s hand control to scroll alphabetically through the list of named stars until you find the one you’re looking at. Press enter on the hand set and the mount will now move to the first star.
- If you’ve set the time, location, and position of your mount properly, you should now see the star within the mount’s field of view either through your finder scope, eyepiece, or camera video. (TIP: Here’s a shortcut to improve the initial setup. Once you’ve aimed at your first star, but before aligning it in the crosshairs with the hand controller, use your mounts manual azimuth and altitude adjustments (the physical knobs) to move the star inside the crosshairs. Once done, you can then use the hand control to align the star, and you will not need to use the arrow keys to move the mount around in this step. All this does is improve the GOTO of the alignment stars during this alignment process. Using the mount’s hand control, follow the directions on screen to center the star in your crosshairs. Accuracy is important here. You want to get the star as centered as possible. Press ‘align’, and then a suggestion for star two should show up.
- Repeat the process for a second star in the western hemisphere. Find a second visible star using Sky Safari, then select the name in the mount’s hand controller to move to that star and align it centered in your crosshairs.
- You will now be prompted to add up to 4 additional calibration stars from the mount’s hand controller. These will all be in the eastern hemisphere, and you’ll want to continue repeating the process for all four of these stars.
- Your telescope now has a an accurate GOTO pointing model stored in it’s system for your specific night sky. The 2+4 alignment process you just finished is not the polar alignment, but the pointing model for the GOTO system. For visual observers you’re set now, and can stop following the tutorial here. If you intend to do imaging, the next steps will cover the polar alignment process to dial in that last bit of precision for long exposure imaging.
- Press ‘Align’ on the hand controller, and use the arrow keys to select ‘Polar Align’.
- Use the scroll arrow keys to move to and select ‘display align’. This will show you (with a reasonable degree of accuracy) how close you are aligned to polar north. An error less than 00 10’ 00’’ is fairly good, but you want to get as close to 00 00’ 00” as possible, especially if your telescope is a long focal length or you expect to use really long exposures. Now use the back button, and select Align under Polar Align.
- You’ll be asked to align your mount to the last star you were pointing at. If this star does not match the criteria required for Polar Alignment, you’ll get an error message saying this star isn’t appropriate, and to pick another star. If you get that error, you need to back out of the Polar Align menu to the home screen where it says ‘ready’, select ‘Stars’ on the hand control, and scroll to ‘Named Stars’. Using Sky Safari, you need to locate a bright star near the horizon, as close to north as you can find, then select it in the hand controller and move the mount to that star.
- Now, press ‘back’ on the hand controller to get you back to the controller home screen, select ‘align’, ‘polar align’ and this will now start the polar alignment process. The scope will now goto the star you’re already pointing at, and it will ask you to center it in your crosshairs. Once you’ve pressed align, it’s going to move once more to that same star, but this time you’ll see it’s not centered again, the scope is now pointing to where it thinks the star should be if your mount is perfectly aligned. The hand controller is going to ask you to now use your manual altitude and azimuth physical mount knobs to re-center the star. Once complete, you’ll press ‘Align’ again. Select ‘Display Align’ to check how close to 00 00’ 00” you are now. Assuming you are at 0 or even a few arc seconds of error, you are close enough to 0 to move on to setting up your guiding software and pick your first target of the evening. If you want to try getting to 0 error, you can repeat the polar alignment part of this process.
Here she is. The 2017 iMac Pro, and my new astrophotography processing workstation. I've just moved up from a 2013 Mac Pro. The new setup includes two Dell P2715Q 27" 4k monitors along with the iMac's 5k 27" monitor. The iMac consists of an 3.2GHz 8-core Intel Xeon W CPU with 32GB RAM. Performance wise, it's about 2x as fast as my previous 6-core Mac Pro. It's connect to both a 6TB and an 8TB RAID storage solution. The 6TB is backup currently, and the 8TB stores all my data and work files.
I'm currently running Astro Pixel Processor on the left display for calibration and integration of captured images. I'm running PixInsight on the middle monitor for processing the integrated images, and I have PhotoShop running on the right hand monitor for last minute color touch up.
This setup might seem like overkill, and it probably is. It's primary use is as my home business graphic design and video system.
Pictured in the setup from left to right is the Dell P2715Q 4k Monitor below that is some Sennheiser HD 650 headphones, a Blu-ray disk drive, the Schiit Audio Asgard headphone AMP and PreAMP. Then the 2017 iMac Pro base model, a 1TB portable G-Drive for transferring images off my 13" 2015 MacBook Pro capturing laptop. A Sphero Star Wars BB-8 robot, World of Warcraft mouse pad, the other Dell P2715Q, and an XBOX 360 controller for games.
Above the monitors is a Mission Chart from when I worked at NASA. It features the mission and communications route for the Shuttle flight STS 51-G. Hanging to the left is a flowchart showing the history of Apple hardware up to the 2013 Mac Pro.
I took advantage of a recent sale on ZWO cameras, and sold my old color camera to move into mono imaging. The benefit of using mono is increased resolution and sensitivity in the camera. One shot color cameras have a Bayer matrix over the sensor which is like a screen door with red, green, and blue filters placed over every third pixel. These pixels are merged into a single color photograph in the software after the image is taken.
In a mono camera, you shoot black and white, and use a individual color filters over the entire sensor so that all of the sensor is shooting in that one color. After you're done imaging, you merge all the colors into a single higher fidelity image. Below is one of my first attempted color images using LRGB filters (Luminance, Red, Green, and Blue).
I upgraded to this Moonlite 2" crayford design focuser for a few reasons. The initial reason was that the compression ring clamp that came with the Explore Scientific scope didn't compress very well. The reducer I have has a beveled edge, and it just wouldn't grab it tight enough. The weight of the camera made the reducer shift in place, which made artifacts show up in my images from the shift. Secondary reason is that the built in drawtube is not very long, which means that to switch between imaging and visual, you have to add and remove extension tubes. With the Moonlite, the drawtube is 4.5" long and can accommodate both lengths just by rolling it in and out to the desired length. No more threading black extension tubes onto a black drawtube in the dark.
Installation was very straight forward. The focuser is collimated at the factory, so I only need to unbolt the 6 hex screws where it meets the OTA tube, and then replace them with the new focuser. Took about 10 minutes. My only gripe would be that I wish they included the allen wrench required for putting in the new screws.
There are a few options you can order. I did the dual rate focuser, with focuser lock, and two vixen style mounts for finder scopes or laser pointers. Additionally you can add a stepper motor and electronic control for focusing from your computer. This is something I'll likely add later, but so far I've not had any issues with losing focus during the night.