pjsmith_6198

Excellent work. Upgrading a focuser can be tricky, especially if you have to perform surgery. I'm glad it worked out so well. Phil

When the Moon is too bright for DSO's, I'll observe double stars and also asteroids. For the asteroids I use charts I make from SkyTools 4 or Starry Nights. These charts have naked eye , finder, and EP views identifying the location of the asteroid. There are always asteroids out brighter than mag 10 out so you can hunt them down whenever the Moon is too bright. I will also practice star hops to DSO targets I want to see when the sky is dark enough. It helps me when I'm trying to see these for real because I'm familiar with the route and I won't be fumbling around as much. Sometimes I I can see my targets when the Moon is bright. Generally galaxies won't be visible but planetary nebulas might be. Especially the smaller ones and not ones like the Helix nebula. They are surprisingly immune from light pollution using OIII/UHC filters. Phil

I've used Newt for the Web when I was building my 12 inch truss Dob. Since it's just for visual use the design goals were a bit different, to use a smaller secondary to get higher contrast for planetary observing and using higher magnifications/lower exit pupil. I didn't need to maximize the 100% illuminated diameter like for AP. But I understand the basic concepts. Newt for the Web is a good tool that's easy to use and the results matched closely with what I finally built. I plugged the original numbers you gave in Newt and got the same result as you - secondary is too small to admit 100% ray. For your new design I didn't know where 100mm minimum focuser height was coming from exactly so I had to study up on the new focuser. I found the manual https://agenaastro.com/downloads/manuals/baader-planetarium-steeltrack-focuser-manual.pdf very helpful. It had drawings and dimensions so I could understand it's geometry. That's a nice focuser. Better than the MoonLite that I used for my scope. After looking, I think you may have only 20mm for the spare focuser in travel. You don't obscure the mirror but the focuser tube goes into the light cone if you don't rack it out 20mm. The of the tube inside radius = 143mm Tube wall thickness is 1mm Primary mirror D = 10"/254mm - Radius = 127mm Focal Length F = 1200mm Focal Ratio = 4.72 From the book "The Dobsonian Telescope - A Practical Manual for Building Large Apertuire Telescopes" by David Krieg and Richard Berry the incoming light cone will be little beyond the radius of the mirror. They gave a formula T ~ D + sin(angular field of view) x F which they simplified to T = D + F/100 For this case T = 254 + 1200/100 = 266mm is diameter of light cone 133mm is radius From the diagram in the user manual, The focuser tube extends 31mm below when fully racked in. Inside tube radius + thickness = 144mm Radius to racked in focuser tube = 144 - 31 = 113mm Light cone radius = 133mm So the focuser has to be racked out 20mm to get out of light cone. The ClickLock S58 clamp is 16mm? I'm not sure how the focuser minimum height adds up to 100mm so I didn't put the numbers in Newt for the Web. Is it feasible to slide up your mirror cell up 35mm and enlarging the current focuser hole for the Baader focuser? That might be easier than cutting a new focuser hole. Phil

I started chasing asteroids a couple of years ago when the Moon was out and made viewing DSO's difficult. I discovered it was kind of fun tracking them down and now whenever I go out with my telescope I'll look for one or two. There are dozens out every night in a broad band along the zodiac constellations. See the attached asteroids_Jan-2021.pdf file. That was printed from Starry Nights 6. It shows what's currently overhead this month. It helps to magnify it make it more readable. A lot of those are too faint to be seen with the normal telescopes we use. The second attachment is a screen spot from SkyTools4. It lists about 30 asteroids from mag 7.3 to 11.8 that are easily visible with the equipment we use. I use charts printed from Starry Nights 6 or SkyTools4 to find them. The charts contain an eye view, a 5 degree finder view which matches my finder, and a eye piece view for the EP I'm using. Sky Safari would probably work just as well. Without the charts I'd have problems anything other than he brightest asteroids. It's interesting to keep track of their general location and magnitudes for comparisons when revisiting and it's also fun to find them two in a view with other asteroids or DSO's . The third attachment is a chart for Jan 21 for asteroids Melpomene (Mag 9.14) and Echo (Mag 10.02). They will fit in a 1 degree FOV EP for a few days and they are bright enough to easily see. Asteroids Hygiea (Mag 9.8) and Echsfeldia (Mag 12.54) is nearby also between M44 and M67. Phil asteroids_Jan-2021.pdf SkyTools4_Current_Bright_Minor_Planets.pdf Echo_Melpomene_1-21-2021.pdf

I observed this comet again last night. It kind of looks like the Crab Nebula. Phil

I think it's worth having if you are into chasing comets as I am. It only helps if the comet's coma or tail is ionized. It filters at the OIII 501 nm line and the C2 511 nm and 514 nm lines. It doesn't help if the comet is just throwing off dust. Actually another way of thinking about it is if you can see the comet without the filter and it disappears with the filter you know there isn't much ionization going on and the comet is mostly dust. Sometimes the comet is faint without the filter and faint or even fainter with the filter. Those comets you know they are ionized because the filter would completely kill it if there was nothing coming through the OIII and C2 lines. There have been only a couple of comets I've only been able to see with the filter. I think the filter works best with the diffuse comets especially when they are near perihelion, such as M3 ATLAS or U6 Lemmon. I watched comet c/2017 T2 PANSTARRS from last November to mid July and for most of the time the filter didn't help at all, but high magnification did. Only when the coma got larger near perihelion did it respond to the comet filter. So it was pretty cool to be able to track it and be able to see when it starts ionizing. Also I think the darker the skies you have the better it will work. I live in a dark red zone and I'm pretty sure I'm missing detail because the background sky is too bright even with the filter. Also try it on emission or planetary nebulas and you'll get slightly different views than with with UHC or OIII. I hope this helps, Phil

I observed M3 ATLAS last night. It was pretty large and diffuse and difficult to see. It's close to Rigel and the location is easy to find. The Moon made it more difficult. but luckily, the Moon will be going away. Best to use a low magnification EP. I have a Lumicon Comet filter and it did respond a bit to that. Made it a little easier but not much. TheLiveSky.com has it at mag 8.6. but it's harder than the magnitude suggests because it is large and diffuse. Phil

This is the time for trying to find Mars Moons. I think Phobos is too close to Mars to see but Deimos is further away, maybe about 2 Mars diameters away. It's a bit faint at about 11.8 magnitude. I've tried a few times but I haven't been able to see it. It was in a position where it was trailing Mars and I was hoping as Mars left the field of view I would have have a couple of seconds without the glare to be able to see it before it to leaves the FOV. Maybe with a little better seeing I'll have better luck. Phil

Fran, Thank you for the kind words. Good luck on your project. It's a very good design and you will have a n excellent telescope. Phil

Hello FranTeryda, You've been given a lot of good advice already. When you buy The SW Explorer 200P are you buying the telescope only or the telescope plus the equatorial mount? Using the rings to attach the scope to altitude bearings is a nice feature. I made a new dobsonian mount for my Zhumell Z10 based on the "instructions for building a Dob" that Louis D provided. That's a very well known site that's helped a lot of people. I made the adjustable cradle th site describes. Once finished, the new larger bearings where much better than the original. Your ring system would take the place of cradle. Give the site a good read it will explain why large bearings are better than small, proper bearing placement, how to balance the scope and basically everything you need to know. Using your ring system and large altitude bearings your design will look very close to the Bresser design that Louis D also provided. Which looks like your original design but modified for larger bearings. AstroSystems have PTFE bearing kits (https://www.astrosystems.biz/pivot.htm) can ship over seas. Click on the Secure Order link the to see if that will work for you. Other alternatives are HDPE (High Density Polyethylene) and there's fiber glass material used in boat repair. Experiment with other materials. Lack of teflon is not a show stopper. The height of the rocker box depends on the balance point of the telescope. The bottom of the telescope needs to be able to clear the base when it's vertical. Add a little more room so you can re-balance the telescope if you add extra's such as RACI finder, telrad, heavy EP etc. Getting an adjustable chair when observing is a good idea. It's more comfortable and you can see more details than when hovering over the eyepiece Phil

Thanks for the excellent write up John. Lots of interesting information there. It must have taken awhile to put together. NGC 2419 is indeed challenging. It took me 3 observing sessions to be able to see it. Only when I saw a photo of it in the DSO-Browser did I see it's location in the EP FOV. The two bright field stars pointing to it. Previously I was focusing on the faint star above it on the sketch above. There was something there but it was popping in and out of visibility. I assumed that was NGC 2419 but under higher magnification it looked stellar. It was right in front of me but I was looking at the wrong target. Once I knew the 2 stars where pointing to it, I was finally able to see it. Phil

I saw it again last Friday 4/10, and it was noticeably fainter than when I saw it a week earlier. I was expecting it to be brighter and easier to see since the Moon wasn't up yet. Instead it was difficult to see. This comet is pretty diffuse and doesn't take magnification well. I didn't see any fragments, just fainter. Phil

A telrad and a 50mm RACI is a very powerful combination for star hopping if your telescope is big enough to handle both. Under my skies which aren't very good, the 9x50 will pretty much match the stars shown in the S&T Pocket Sky Atlas. I have a clear plastic overlay with a 5 degree circle matching the PSA scale so what I see within the circle matches what I see through the finder. That combination has helped me more than anything I can think of. You can do the same thing with the 6x30 finder but you may lose some of the fainter stars but it's still way better than not having a RACI, Phil

Both are very small. Under low magnification they look very star like. You may have had them in your field of view. Jim gave excellent advice. Find their exact position with an app. Then increase the magnification until you see them as tiny disks. Uranus is about twice the size as Neptune, but Neptune even under high magnification looks only a little bigger than this period "." Sort of like one of Jupiter's moons. To my eyes, Uranus is kind of grayish green but Neptune is a definite blue. After you see them the first time, it's easier to see recognize them. Phil

The Alt pivot should be located on the OTA's center off mass. So measure from the midpoint of alt bearings to the end of the tube. Then add a couple of inches in case you add a RACI finder and or heavy EP's in the future so you can re-balance the scope. Do you have azimuth bearings? I have a Z10 which I re-built the mount based off the Stellafane.org design here https://stellafane.org/tm/dob/mount/index.html because I added a 60mm finder , a telrad, and used heavy EP's. I couldn't adjust the altitude bearings enough to balance the scope. I found the large bearings worked better than the stock bearings. But if you have working alt bearings and don't have extra stuff on the front end you can just copy the existing mount design as long as you have the azimuth bearings. Phil

I last saw it on 11/25/2019. It's still pretty faint, but I was able to see it with a 20mm EP (62.5x). So it's getting brighter. I first saw it a couple of weeks earlier and it was not visible with the 20mm and only appeared as a small puff of fog in a 7mm or under. On the 25'th, with a 6mm EP it looked like it had 2 central condensations. One was the comet and the other was a mag 13.6 star that it was very close to. I watched it long enough to see the comet move away from the star. I verified with Starry Nights afterwords to confirm what was going on. The coma was not round, but it didn't really look like a tail. It did look very much like a galaxy. I tried a comet filter but it wasn't very responsive to it. It didn't kill it, but it didn't make it easier to see. The SkyLive.com has a observed magnitude of 10.3. It's about a magnitude better than it was. When you find it, try higher magnifications, you can see more detail. Phil

I had a couple of clear nights and decided to give these comets a try. The Sky Live site had these comets at magnitudes 11.4 and 11.6 respectively and I wasn't expecting much but surprisingly both were visible. They were both small faint puffs, but small faint puffs not difficult to see. I thought they were easier to see than Comet Africano. I was using my Z10. They weren't visible with a 20mm EP but started seeing hints of them with my 8mm Delos (156x) and was able to confirm them with 6mm Delos (208x). They are both small, around 2", but are fairly condensed so are fairly easy to see. The Moon will be interfering for the next couple of weeks but they will be around for awhile in very good position. C/20128 N2 is now in Andromeda, is near M31 and will reach perihelion in mid November then start to fade. C/2017 T2 now in Auriga, between M36 and M38 will reach perihelion in early May 2020. It may reach naked eye visibility before it starts to fade. This will be in Auriga for the rest of November, then go through Perseus, Cassiopeia, Camelopardalis and be in Ursa Major in June. There will be 6 months to observe this and it will be in excellent position the whole time. Here is Seiichi Yoshida's Weekly info about bright comets http://www.aerith.net/comet/weekly/current.html . Phil

I think you are right. You were training yourself to see faint threshold objects. The more you observe, the more you will see and the more confidence you will be able to even fainter objects. When I started observing I could only see the brightest DSO's. I started the Messier list, I thought there was no way I could seem them all since I was having trouble with objects like M65/M66, but I kept at it pushing my limits to see these things and I finished the list. And that gave me confidence to do the Herschel 400. The funny thing is, I had more problems with the Messier's than a lot of the Hershel's. Training yourself as an observer is like training as a runner. Some days you train hard doing intervals on the track (or looking for very faint DSO's) and other days are easy runs (or observing your favorite bright DSOs) The important thing is just to run/observe consistently. Phil

I've viewed this this comet 5 times in the last couple of weeks using my Z10. I've found it to be pretty challenging overall but it seems to have gotten brighter without the Moon. John's observation of it looking somewhat fainter that Mirach's ghost was spot on. I was looking at both last week when they were so close together and compared them and I was thinking the same thing. It's tougher than the estimated 8-9 mag indicates unless you have dark skies. The comet is pretty diffuse and in my dark red skies I'm only seeing the central condensation. I think that's why my best views I've had with it have been with my 8mm and 6mm Delos. SkyTools 3 estimates it as mag 8.9 and a size of 6.9'. That's pretty big but I have trouble seeing it with low magnifications. I've tried my Lumicon comet filter and it had a mild response. It didn't make it much easier to see, but it didn't kill it either. The comet is moving very rapidly now. When looking at it with a 6mm EP, you can see it move with repect to the field stars in about 10 minutes Now is the time to look for it because it's at its brightest plus it will be moving south very rapidly. It will be in Pisces Austinus by mid October. Here is some charts and info on it. http://www.aerith.net/comet/catalog/2018W2/2018W2.html http://www.aerith.net/comet/future-n.html https://theskylive.com/comets Phi

I’ll have to give that one a try. I’ll probably need a darker site. If I’m able to see that, I may be able to see Pluto in Sagittarius. That is about mag 14.3 but it’s low on the horizon. Not too far from Barnards galaxy Phil

Here's a link to an article and a list of 12 quasars that are currently visible. I just observed 3C-273 for the first time about a week ago and was looking for others to find then this just comes out. What luck. Seven of them are mag 14.1 or under so these seem to be do-able. The furthest is HS 0624+6907 mag 14.0 in Camelopardalis 4.56 billion light years. That's probably the farthest thing I'll ever be able to see with my Z10. The light from that is from back when our solar system was forming. Pretty amazing. Anyway, here's the link https://www.skyandtelescope.com/observing/12-quasars-for-spring-evenings/ Enjoy Phil