Focusing is everything. Without focus, your photos will look really bad. Without good focus, your autoguider will not function properly. Without good focus, you won't be able to enjoy what you're viewing. And sometimes things are out of focus on purpose (nebulas).

Sorry for all the repetition on this page. I took a lot of the things that are in this page from some of the other pages. I added them where they were relevant so you don't have to go looking around.

Click on any image to see an enlarged version.

Telescope Focusing Ok, in terms of just looking through the telescope for visual observation, there really aren't that many things that cause bad focus. Of them, there are the focus knob (duh), fog/frost, and clouds or bad weather. Let's get the obvious out of the way. If you don't have good focus, you don't have good focus. Turn the focus knob, and see what happens. :) Bad weather can happen. You can be so engrossed in something, that you don't even realize your subject is now covered by a cloud. That happened the other night. I was playing with my new webcam, and the moon all of a sudden got really blurry. That was weird. I looked up, and there was a small cloud covering it. Nothing else in the sky but this stupid little cloud. DUH! Also, before I forget to mention this- some things are blurry. If you're really new to using a telescope, it will be helpful to know that if you point your telescope at a galaxy or a nebula, you're not gonna see what you see in the hubble pictures. The best views of nebulas will appear out of focus. Take the ring nebula for instance. If you look directly at it, you won't see it very well. I suggest you focus your optics on a few nearby stars. Then, to view the nebula, look slightly to the left or to the right of it. Your peripheral vision is very sensitive, and you will be able to see the nebula better that way. This is called averted vision. This article focuses on focusing. Same disclaimer as with all my articles- I do not claim to be an expert. There are plenty of those out there. What I offer to you is my experience. Hopefully you'll get something out of this. If not, it's my journal and I can refer back to it whenever. By the way, this article is definitely a work in progress. I am learning something new every day, so be certain I will be adding to this... You'd be surprised how many times I was looking at an object through my scope and wondering why everything was so blurry. No matter how many times I tried to focus, it wouldn't get any better. It was then that I realized the scope was either fogged or frosted over. It's an easy thing to forget. There are several ways to battle frost and fog. One is a dew heater or dew zapper. This is some sort of heater band that's strapped around the end of the optical tube assembly and keeps it below the dew or frost temperature. Sometimes the temperature is so cold that even with the dew heater on max, it will frost somewhat. For this, I have a backup dew removal system-- a hairdryer. A few seconds of the hairdryer on a mild setting (never high heat) pointed near the corrector plate, and the dew and/or frost is gone. Another method of getting rid of dew/frost is by using a dew shield. There are two main types- hard and soft. Hard ones are nice because they're already molded to the right size and shape. The soft ones are nice because they can be rolled up into a very small size for storage. On most nights, one or the other will work fine. However, sometimes it's really cold or really moist out, and you may need to use the dew zapper and the dew shield to keep your OTA from fo31/Dec/2006 19:04gging or frosting up. Not only do you need to keep the corrector plate from frosting or dewing over, you also need to do the same with your eyepiece. I missed that one a few times too. "Hmm... the corrector plate looks fine". DUH. The eyepiece is foggy. They make dew heaters for eyepieces as well. I have the Kendrick Dew Removal System. It's a heater unit with several bands or patches that heat up a few parts at the same time. So you can have one heater for the corrector plate, one for the eyepiece, one for the guide scope, and one for the telrad finder (if you have one, and I highly recommend one if you don't). You can read more about the kendrick system, and see photos of it on my equipment page. Kendrick Dew Removal System Heater Controller. There is room for up to four heater straps. I have three. Kendrick Dew Removal System Heater Straps. I have one over the corrector plate, one around the finder, and one for the telrad. My Backup Dew Removal System (a hairdryer). Sometimes, even with the dew zapper, moisture forms on the corrector plate- this happens more commonly in winter where it frosts up. A hairdryer is very effective in eliminating dew and frost. I have found that by using the dew zapper along with a dew shield, there is almost no dew, even after being out all night in 20-degree weather, so I haven't had to use this in awhile. Film Cameras This is where I will babble on for hours about film cameras... Peak 8x Lupe converted into a magnified viewfinder. Focusing on a camera through a telescope is a VERY difficult thing to do. Fortunately, there are some ways of getting around this. Some day I plan to write up documentation on how to build one of these. It just takes a little patience, a dremmel tool, and the lupe. This is the rectangle model, which is very close in size and shape to the prism channel. With this configuration, the view of a deep space object is a little dimmer than if I were using a cheap MA25mm eyepiece. The Beattie Intenscreen Plus focus screen with etched gridlines. This isn't exactly a cheap shortcut, but it sure makes life easier when focusing an SLR film camera. I got this model over the clear model for two reasons- 1) the etched lines on the screen aid in making sure the lupe is focused properly, and 2) it aids in centering my target object in the viewfinder. Modified Hartmann Mask. This mask is used to creat multiple images of a star or bright object in your eyepiece. When you see more than one image, it's out of focus. When they're intersected, it's in focus. Take a piece of cardboard or manilla folder, and make a solid circle a little bigger than the end of your optical tube assembly. I just traced the cover. Then, make two circles opposite each other, that are about 1/3 the width of the optical end. Keep in mind, you have to avoid the center mirror obstruction. Then, in those circles, draw small slits across the diameter of the two circles, but make 90 degrees akew each other. With an x-acto knife, cut the slits out. The mask should look like the picture to the right. Tape this mask over the outside of your OTA, and point the scope at a bright star. If the scope is out of focus, you will see two slits, one horizontal and one vertical. As they come into focus, they will make a cross like the image to the right. When you see the cross, it's in dead focus. This type of mask is called a modified Hartmann mask because the original hartmann masks were just dots. A good example of this type of focus mask is the Kendrick Kwik Focus mask. You can see mine here. The three-dot version is pretty acurate, but the ones with only two dots are so-so. With the slit modification, you can get very precise focus because you know exactly when the lines intersect in the middle. You can use this method directly through the viewfinder of the camera, but by using the image preview with magnification as described above, you'll get a great focus. Digital SLR Cameras This is where I will rave about how great Digital SLR cameras are... Digital Camera Preview Screen with Zoom. I'm going to be writing an article on focusing, since I've spent a lot of time and effort learning how to do it well (and I'm still learning, believe me). But until then, here's another great focusing technique with a Digital SLR camera. Get the subject to where you believe it's at a good focus through the scope. Take an exposure that's about 30 seconds long. Then pull the image up in preview mode, and do a digital zoom to the highest magnification. This works great, and when used with the modified hartmann mask below, you'll get a great focus every time. The downfalls to this technique are that you are touching the camera while you're doing all of this, and the screen is typically very bright, so it may affect your night vision. Nikon F2 body as a focuser for DSLR camera. Since I got the D50 DSLR camera, I haven't used my F or F2 once. It's sad, really because I bought that camera when it was ~15-20 years old, and it cost me $260 for the body alone. Now that everything's going digital, you can get these for less than $50. So it's a shame to get rid of it, and it just sits in the camera bag. As I said before, focusing a camera through a telescope is a difficult thing to do. This setup was awesome. And you know what? This setup is parfocal to my D50. So, I can snap the F2 with the intenscreen and 8x Lupe onto the OTA, focus, then put the DSLR back on, and it's a really sharp focus. Works great! Infrared Remote for DSLR Camera. even though this isn't exactly to do with focusing, it can certainly affect how your images turn out. In the past with film cameras, I had a bulb cable attached to the camera body. When you want to snap a photo, push the end of the cable, and it locks with the mirror up. Click the end, and it releases and your photo is done. Problem number one with this arrangement is you're touching something directly attached to the camera. Even with a delicate hand, you're still moving the camera. The Nikon D50, and I'm assuming many other DSLR cameras, have an option for a wireless remote. This is fantastic. You can set the camera on a remote timer, so you hit the button, it will open the shutter, wait 5 seconds, then start the exposure. This is great, because even the movement from the shutter is dampened in 5 seconds. Hit the remote a second time, and it closes the shutter. This remote cost me about $10 on ebay. It's not the real Nikon remote, but works just as well. Web Cams Wonk wonk wonk.. Stuff about webcams. yadda yadaa... A web cam for astrophotography? You're probably thinking it's cheezy using this cheap little video camera for astrophotography, but I'll tell you, I don't think I've ever seen images from film or DSLR from an amateur home observatory that rivals some of the photos I've seen made by a webcam. The way it works is, the webcam takes a constant video stream of maybe 10-20 frames per second. You take that movie file, import it into some software, and the software digitally stacks and averages the images to make a super-crisp image. You can see some of the photos I've taken in the astrophotography section. I bought the Philips ToUcam Pro II 840k. It's one of the more expensive ones (a whopping $80), but is a higher quality than your typical webcam, and is one of the most popular in use right now. I've also heard that people are using webcams as autoguiders with software like Guide Dog. I have an ST-4, so I haven't tried this yet. Autoguiding I can talk for hours about how I never got this autoguider working, and I never got that autoguider working, etc... And I will. Stay tuned. ST-4 Ronchi Focuser. This one was made by STI. This isn't exactly a cheap shortcut, but it sure makes life easier when focusing an ST-4 autoguider. I plan to write up an article on the ST-4 some day, and how freakin' impossible it was to get it to work. Focus is absolutely critical. And focusing an ST-4 is really hard. This thing is a parfocal focusing screen. That is, take an eyepiece that's also parfocal to the ST-4 (I have a 20mm that's parfocal). Center a guide star in the eyepiece, and focus. Then take the eyepiece out and put this ronchi focuser in it's place. Now you're doing a fine focus. As you get closer to focus, the bars start getting fatter and fatter. Once you get to where there are no bars left, you're in perfect focus. Take the ronchi out, replace it with the ST-4, and you have a perfect focus. It's a whole lot easier than eyeballing it and doing it by readings on the ST4. Crayford and ZIF focusers I don't have any experience with these, but it wouldn't be right not to at least mention them. These focusers are put in front of your eyepiece or camera, and are a much finer focuser than the standard SCT focuser. They make motorized version that can tie into focusing software to basically make your focusing perfect. I don't have the kind of cash to put out to get one of these. Someday, maybe. For a decent system, you're looking at $450-600 or more... Software and Miscellaneous I just wanted to mention that once you get the photos into the camera or onto your computer (DSLR and webcam), that's only half the journey. Then you have digital processing to do. That's where you stack your images, average them, process them this way and that, clean them up, etc... There's lots to say about Photoshop, Images Plus, Iris, Maxim-DL, MaxDSLR, and a slew of other packages, but I couldn't do it justice. This is one of those places where you're just better off buying a good book. I suggest A Guide to Astrophotography with Digital SLR Cameras by Jerry Lodriguss. This is the most comprehensive source of digital astrophotography, and includes a wealth of information on digital processing using several software packages. There are a ton of video demos on the disc as well. I believe Michael Covington is also in the process of writing a similar book. Oh, and specific to focusing, there are packages out there that assist in focusing like DSLR Focus, Maxim-DL, and a bunch of others. Mirror Shift Stabilizer. Again, another item that's not exactly to do with focus, but if you have a subject you're shooting near the zenith, you run the risk of mirror shift. That is when the primary mirror moves during your shot. With SCT's, they have a tendency of doing this. This little gadget is screwed into the hole where the original shipping mirror bolt was. It's used to put tension on the primary mirror to prevent "mirror flop" during long exposure photography, especially near the zenith. Now, I've seen this a few places, but I have to believe that Chris Vedeler invented this device. He doesn't sell it, he gives you the plans to build your own. How cool is that? Click Here to check out his page, with plans. Links Some links to other pages that have to do with focusing... Nikon D70 Manual Focus Aids As I find more, I'm sure I'll add to this list.