Can the Sunday after International Observe the Moon Night be known as Carefully Observe the Sun Day? Maybe we shouldn't encourage the general public to observe the sun, that could turn bad. But anyway, I had gorgeous clear skies today and had a busy and fun morning working on solar projects! I don't observe the sun all that often. Check it out, each of the active regions (sunspots) are the size of the Earth!
Canon T5i single frame prime focus on Meade 285, ISO 800, 1/60 sec, 900mm
I find it much more challenging than observing the moon for a few reasons: You can't look at the sun to line up your telescope - I ended up slewing around hoping to stumble upon it in my eyepiece. Viewing your camera's LCD screen in the daytime is terrible - and if you rely on it to focus like I do, this becomes extremely challenging.
I modified my homemade DSLR solar filter to fit over my telescope. This is my first solar image at prime focus, and it was my first time observing the sun through my telescope eyepiece. Here are some more photos from today:
My solar observing setup with Canon T5i at prime focus on Meade 285 with homemade solar filter
I noticed the finder scope was producing a scary looking magnified dot of light, and I imagined a magnifying glass burning a hole in my shirt while I looked through the telescope. No thanks! While it didn't look like the dot was too hot, I covered the finder scope with an eyepiece cap just to be safe.
Here is my homemade solar filter attached to the telescope. The tube is a good fit, but I added some tape just to make sure it wouldn't blow off while I had my camera attached to it. I'll go into more detail about the modification to my filter in a separate post.
DIY solar filter anchored with tape so it doesn't blow off and ruin my camera or blind me in one eye.
There's a trade off between the resolution of the sun at prime focus, and the ability to carefully control focus with the Canon T5i focus controlled by my laptop. So what's more important? A larger disk size but clunky manual focus out in the sunlight where it's hard to see anyway? Or careful laptop focus controls but smaller disk of the sun?
Canon T5i with 300mm lens and solar filter connected to my laptop with EOS Utility
Canon T5i 3 frames stacked in Registax, ISO 400, 300mm, f/9, 1/250 sec
I think the resolution wins and the prime focus is a little nicer even though it's not as sharp, it looks more natural even in one frame without stacking. What do you think?
Compare prime focus sun (left) vs DSLR at 300mm stacked (right)
I've been celebrating International Observe the Moon Night since 2012, and even if I don't have it marked on my calendar, I've coincidentally been observing the night sky on the observation of this day every year. I think that's the point, right? It motivates you to get out there and do some observing, or in my case astrophotography.
Tonight, I tried to do a quick prime focus shot using mirror lock up with my Canon T5i. The problem with mirror lock up is that it takes so long between frames, it confuses Registax. The good thing is that the mirror doesn't shake my telescope on this ancient (15 year old) EQ mount.
Here's my best attempt in about an hour while dinner was being made. Everything from focusing to cropping in Camera RAW, to stacking, to Photoshopping all in a short amount of time.
Canon T5i 14 frames stacked in Registax, ISO 400, 1/125 sec, prime focus Meade 285 900mm
Chris asked me, what would happen if International Observe the Moon Night fell on a new moon? Well, my guess is that it doesn't, the date seems to change to make sure that the first quarter moon is high in the sky.
InOMN is usually held in the fall, when the Moon is around first quarter. Fall in the Northern Hemisphere is generally a good time for InOMN, because of school schedules and the weather, and a first quarter Moon is visible in the afternoon and evening, a convenient time for most hosts and participants. Furthermore, the best observing is typically along the dusk/dawn terminator, where shadows are the longest, not at full Moon.
This day has only been celebrated since 2010? I say let's keep it going! Great excuse to get outside or to hold an event for the public!
I don't have many prime focus attempts under my belt - in fact if you search for "prime focus" on this blog, you'll only come up with 3 posts of the moon at prime focus, and a couple Jupiter, and a couple double stars. In fact, I don't believe I've even attempted the moon at prime focus since I upgraded from the Canon Rebel XT to the Canon T5i. After some major issues a while back, at least now I have my go-to prime focus attachments using a T-ring --> T-thread to .965" --> .965" threaded collar setup.
As I've noted before, the hardest part of photographing the moon at prime focus with my Meade 285 refractor is the clunky focusing wheel on the telescope. The focuser is plastic, and there is no fine focus adjustment. So, as you can imagine, when looking at the LCD screen on the back of the camera and adjusting the focus, it's nearly impossible to tell when I'm actually in focus... Whenever I touch the telescope the image jumps all over.
With all that in mind, the advantages to prime focus are that you get a much larger image (and therefore higher number of pixels in the diameter of the moon) compared to just a 300mm camera lens. Prime focus definitely has the potential upper hand, but a major handicap when it comes to focusing - whereas the camera lens has incredible hands-free focus, but the moon is only projected onto a tiny area in the center of the image sensor and thus a smaller diameter in real pixels.
I took the images below on Sunday, September 11, 2016.
Click to enlarge, prime focus vs 300mm camera lens
Now many it's not completely fair, the 300mm moon on the right is far from my best attempt. I only stacked 10 frames in Registax, which was having a rough go of it on Windows 10. When I finally got it to stack without crashing, I noticed the alignment wasn't quite right, but it still does a nice job showing the huge difference (3x the diameter) in relative size.
Stack of 10 frames, Canon T5i at 300mm, ISO 100, f/9, 1/160 sec with High Pass layer in Photoshop
Stack of 17 frames, Canon T5i prime on Meade 285, ISO 400, 1/250 sec, 900mm with High Pass layer in Photoshop and Exposure +1.0 in Adobe Camera RAW
From my perspective on the patio
During my observing session, I also saw the rings of Saturn through the Meade 285, which is always a treat - even though it is insanely frustrating to try to position this old mount that doesn't want to stay put once you have your target. I also tried several times to get my iPhone mounted on the eyepiece to take a video of Saturn, but the mount is just too finicky and shifty.
Finally, I took this quick timelapse video of my prime setup using the app Hyperlapse, which is convenient when you don't know how much you will want to end up speeding up the final video. Unlike the other timelapse apps where you have to set the speed at the beginning.
I wish I could show you what I saw with my eye (said every photographer ever). I observed Jupiter through my Meade 285 refractor (60mm, 2.4") last night. I was able to visually make out two red stripes on the face of a pale yellow orange dot. At something like 35 arcseconds in diameter, this might not be the ideal time to observe Jupiter - but it's still larger than Mars at only 15 arcseconds in diameter.
Because my camera takes 1080p video, the single frames are actually much higher resolution. I was able to see a faint dark cloud band in a single frame (not as good as with my eye through the eyepiece). My 6mm eyepiece focuses the light further away from the eyepiece, which is great for people who wear glasses so they don't have to press their glasses up against the eyepiece. However, this makes it harder to hold an iPhone over the eyepiece because you have to hover in mid-air rather than resting the phone on the eyepiece.
Canon T5i attached to my small telescope with T-ring and .965" to T-thread adapter
Looking at Jupiter down the barrel
Single frame (not stacked from video), one dark cloud band visible
Stacked from 1080p video at prime focus (just a blob)
Single frame at ISO 6400 compared to Stellarium screenshot
I got some more experience at prime focus this past week, mounting my DSLR directly to the Meade 285 using the telescope as a huge lens. I was able to improve upon my best Albireo photo - previously I shot it using just the 300mm lens on the DSLR, which is able to resolve separation distances of about 28 arcseconds. At prime focus, the separation is much more apparent, and there is some black space in between which helps the color difference show up a little better.
I also turned my scope to Venus, and was able to identify its current crescent phase - however the chromatic aberration is quite apparent on this old refractor. Notice how the red and blue ends of the light spectrum don't quite line up - which means the lens is effectively acting like a prism when it is not supposed to.
I made another moon attempt at prime focus last week and the results are frustrating. I just can't seem to get the entire disk in focus at the same time, and although the moon is much higher resolution at prime focus, my best clarity still came from digiscoping with my iPhone through the eyepiece.
So I either need a camera with live view so I can focus on a larger display (or a laptop) rather than through the tiny viewfinder, or an iPhone mount / adapter for the eyepiece. Or maybe video is just the way to go, and stacking 20 frames won't cut it at higher resolutions. Since my DSLR doesn't do video, this is still a problem.
Canon Rebel XT (350D) at prime focus on Meade 285
Crescent moon at prime focus, 20 frames stacked in Registax
This weekend I packed up all my gear and headed over to my friend John's house north of the city. It's not exactly dark skies, but there is a lot less light pollution from direct glare (but still can't escape the sky glow on the horizon). My goal was to photograph the moon, try to spot Andromeda through my scope, and then maybe check out some objects on the September list or just show John some double stars that I'm already familiar with.
232 images stacked in StarStaX, taken with Canon Powershot at ISO 800, 15 sec each
DSLR at prime focus on Meade 285, 1/50 sec, ISO 200, stack of 20 images
DSLR on fixed tripod, 196 subs, 44 darks, 42 bias, ISO 1600, f/5.6, 1.3 sec, 300mm
I started by showing John how I set up my point and shoot to take star trail photos. We got this camera up and running first so that it could go the whole night while we were looking at other objects. Next, I went to the moon because it's such an easy target. We observed the moon, and then I tried to find the Andromeda Galaxy by star hopping. I still couldn't locate it with my scope! It must be too faint, and I must be too inexperienced.
After getting frustrated about Andromeda, I tried an easier target - I was able to find Albireo and showed John the color contrast between the two stars. Next, I tried to observe Beta Cephei, but I still couldn't resolve it into two different stars. I either had the wrong star, or my magnification (or resolution) just isn't high enough to split them.
I was, however, able to split Mizar and Alcor very easily. I put my camera back on the scope to take a few shots. I didn't notice it until I got the images onto my computer, but it looks like I actually got Mizar to split into its two subsequent stars (each of which are actually double stars themselves!). Tons of fun and quite the prolific night of observing!
ISO 1600, 1/3 sec, Canon Rebel XT at prime focus on Meade 285
Mizar A/B have a separation of 14.4" (arcseconds) which I guess is about the limit of my setup
In an earlier post I wrote about buying my first t-adapter to try to hook my camera up to my 60mm Meade refractor. The basic problem was that I couldn't reach focus even though all the pieces fit properly - the issue being that I had the focuser all the way up against the optical tube and was still not quite focused. I had to find a way to shorten the length of my adapters to give myself more room to focus.
I bought a .965" to t-thread adapter and was initially shocked with how big this thing is! It looked a lot smaller in pictures. This adapter was longer than the t-adapter that slides into the eyepiece, but I thought maybe since I could do away with the diagonal mirror it would still be short enough. (I was wrong).
I took my telescope and my entire set up to an Indiana Astronomical Society event to try to get some guidance. I was able to borrow a Barlow lens from another member, which seemed to help but I still couldn't quite get to focus. I had to daisychain all of these adapters and eyepiece cups together and it was still too long.
The next day I took a more critical look at the pieces that I already had to work with. I was pretty sure that I already tried every combination of pieces that came with my adapters, and I remember laying them all out on a table to see if I could get it to work. With fresh eyes I noticed that the smaller and of the .965" adapter unscrewed and I thought to myself the threads must be T threads because the entire tube is the same diameter.
Camera body --> T-ring --> T-thread to .965" --> .965" threaded collar
.965" to T-thread camera adapter (too long, I used just the piece on the left)
Collar screws onto the focuser tube and slides over the .965" male
A look at my prime focus setup. I was in focus at this distance (with an inch or so to spare on the focuser)
Prime focus in the field (I was so pumped!)
I went outside with this super short configuration and what do you know, it works!
I'm trying to take the next step with my astrophotography, and that means utilizing my Meade 285 2.4" 900mm refractor. In order to do this, I need a way to mount my DSLR onto the telescope. I've heard of t-rings and t-adapters, and it seems pretty straight forward. The t-ring connects to the DSLR where the lens would normally attach - and therefore, you need to get one that corresponds to your type of camera (in my case Canon EOS).
Ok, so the t-ring is specific to your camera, but the t-adapter is a universal (I think?) thread dimension. The other side fits into a 1.25" eyepiece holder.
T-ring and t-adapter assembled on Canon Rebel XT
T-ring for Canon EOS type, and universal 1.25" t-adapter
T-ring fits snug into lens coupling, and locks with the lens release
Ok, so everything was hunky-dory, and I got my t-ring and t-adapter connected to my camera. Last night, I took my telescope out to try to focus on Venus. I couldn't get Venus to focus. I tried taking my focuser tube all the way out, and all the way back in. It seemed to get the closest when I went all the way in, but it never got focused - not even close!
My setup that did not achieve focus. I think it's too long, so I'm going to cut out some pieces.
I had my t-adapter nested into my 1.25" eyepiece holder because that's the only way that everything seemed to fit together. I tried taking my diagonal mirror off, and my other bits and pieces of tube and connectors - what a mess! I was trying to find a way to shorten my setup, because I figured that would compensate for my inability to focus any further 'up' the focuser tube.
Venus out of focus at the limit of my focuser (butting up against optical tube)
I finally looked up my telescope manual and read that my focuser tube is .965", which seems to be a smaller but somewhat common dimension for these low power scopes. So the issue is that my 1.25" thread t-adapter barrel (aka female) won't screw directly onto my .965" thread (aka male) focuser tube.
I also got some feedback on Instagram that I should get a Barlow lens, because not only will it give me about 2x magnification, but it will change my prime focus distance from the optical tube to within a range that my focuser can reach. I think I'll hold off on that until this guy comes in the mail. I'm not sure where a Barlow lens would fit exactly, and if they make a .965" to t-thread Barlow. I feel like I'm playing with a really expensive LEGO set and the pieces aren't matching up!
As a consolation prize, however, I'm pretty sure my out of focus image of Venus corresponds to the phase of Venus last night, so that's pretty neat.
I'll post updates here as I try to figure this out...
