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Found 20 results

  1. [A few more photos are in the imgur album] Made this telescope for observing sunspots. The Sun gets projected onto a piece of paper after bouncing from 3 mirrors inside the frame. It's compact, light, takes only a few seconds to point at the Sun, and sketching sunspots is as easy as circling the spots on a piece of paper. It can even project the Moon: The design is inspired by a commerically available telescope, but I’ve done all the designing myself, just for the fun of it. Sunspotter is full of little details that make it interesting. How do you fix the eyepiece in the exact place where it needs to be? How do you keep the lens in place and perfectly aligned? Building the telescope was a lot of fun, I’ve learned to use a jigsaw, X-Carve and a 3D printer. The plan is to use it to complete the Astroleague Sunspotter Observing Program, but unfortunately I completed it at the minimum of a Sun cycle, and won’t see any sunspots until next year. Telescope parameters: Magnification: 75x Size: 41cm x 41cm x 15cm Weight: 1kg Design: Keplerian Projection size: 75mm Materials needed: Lens: Ø52mm f=750mm achromatic doublet Mirrors: 1, 2, 3 Eyepiece: Baader 10mm ortho 1.5m² of 10mm plywood Wooden glue 5m of PLA filament 12 nails Compressed air Isopropyl alcohol Tools I used: Jigsaw with a 30° bevel capacity X-Carve 1000 3D printer A laser pointer Clamp Learned modelling basics in: LibreCAD Easel TinkerCAD Fusion 360 Part 1: Choosing the lens The idea of a sunspotter is that the light goes through the lens, travels inside the telescope, bouncing from 3 mirrors, enters an eyepiece and the image gets projected on one of its sides. The distance the light travels before entering an eyepiece is the focal length and it determines the size of the telescope. I chose a Ø52mm f=750mm achromatic double. Observing the Sun doesn’t require a large aperture, 50mm is more than enough. I wanted a high magnification and went for the longest focal length I could find, which was 750mm. Achromatic doublet design is what people use in refractors. If it is good enough for a refractor, it’s definitely good enough for my project. With the focal length chosen I could design the wooden parts. A drawing showed that the frame needed to have sides 30cm long, but I wasn’t sure about the placement of the mirrors and went for 31cm sides, planning to shorten the light path as needed by adjusting mirror positions. This is the LibreCAD drawing of the layout of parts on a piece of plywood: Part 2: Building the base Having a drawing of the base in LibreCAD, I printed the drawing 1:1 scale on multiple A4 sheets of paper and glued them together. I transferred the drawing to a piece of cardboard and cut it out. Applied this cardboard template to the sheet of plywood, and cut out two parts with a jigsaw.. I’m not an experienced user of jigsaw, and couldn’t manage to cut half-circles accurately enough. Even worse was that the two parts were very different. I didn’t want the frame to randomly tilt left or right when adjusting its altitude, and had to spend a lot of time with sandpaper to make the halves as similar as I could. Glued the two large parts with three small parts in the middle. Additionally nailed the parts and the base was ready. Part 3: Frame The frame is simply a triangle made of three pieces, with short sides cut at a 30° angle. Most jigsaws can cut at 45°, but not at 30°. Had to buy a new jigsaw with a 30° bevel capacity. Cut out three sides, cut short sides at a 30° angle, but didn’t put them together just yet. The lens needs to be perfectly aligned with the Sun-facing part of the frame, otherwise the Sun projection isn't circular but elongated. My solution was to carve a hole with a little step as shown on the image. The inner hole is Ø46.5mm, the outer hole is Ø50.8mm. The outer hole is the exact size to let the lens fit, but with a little bit of friction. Had to carve several holes to find the minimal size the lens could fit in. The step is just large enough to have enough surface for the glue to keep the lens in place, I didn't want to reduce the aperture too much. I used an X-Carve for carving and Easel for modelling. With all 3 sides ready, I could assemble the frame. It appeared that my 30° angle cuts were not very precise, but after some sandpapering the sides started fitting together alright. Glued the parts together and left them to dry for a day. To apply some pressure on the joints, I wound several twine loops around the frame really tight, made sure all sides fitted well together and left it to dry like that for a day. Part 4: Mirrors When selecting mirrors I was looking for the smallest mirror that fit the cone of light. Small mirrors are a lot easier to place, and they let me better control the length of the light path. I considered using elliptic mirrors, but they were bulky and really hard to place. All mirrors are first surface mirrors, otherwise planning their locations would be a lot more confusing. This was my original plan of placing the mirrors: As you can see, all the angles and distances were carefully measured, and I wanted to simply make mirror holders of those exact dimensions. This was clearly a bad idea. I 3d-printed some parts like this: And only later I realized that the frame angles are not exactly 60°, and that there are drops of glue along the edges that don’t let me fit the pieces deep enough in the joint between the sides. I cut angles from all the mirror holders: After I put the first mirror in place I realized the angles are all wrong, and that I needed to re-do the holder. Separating the mirror from the holder was a huge pain, which resulted in an accident. The mirror fell off the desk and got damaged. Luckily, only the back side got damaged, the front side was still working: The final designs of mirror holders looks like this: The holes in the front surface let me apply pressure on the back of the mirror if I ever want to separate it from the holder. The recesses collect the excess glue to avoid mirror skewing when gluing them. All other holes are simply to save the filament. Part 5: Placing mirrors What I learned is that you can’t plan positions of several pieces with high precision and just hope that it all comes together. I needed a feedback about the precision of mirror positions. I used a laser pointer to verify mirror positions at each step. In the picture you can see that the laser is firmly set in a hole in another piece of wood, with layers of isolation tape on the tip of the laser pointer to make it stable. A clamp holds the piece of wood in place, ensuring that the laser ray goes in the same direction as a solar ray would. A crosshair of black thread at the center of the lens ensures the laser goes exactly through the center of the lens. When placing each mirror, I marked the spot where I expected the laser to end up. While gluing the mirror holder to the frame, I kept the laser as close to that spot as possible. If for some reason, the laser couldn’t hit the expected spot, I did my best with placing the mirror, and recalculated locations of the following mirrors. I saw the first sunspots after placing all the mirrors and simply holding an eyepiece in hand. Part 6: Eyepiece holder I tried eyepieces of different focal length and liked the picture I got with a 10mm eyepiece the most. An eyepiece needs to be in a very exact spot to produce a sharp image. At this point it was obvious that my frame doesn’t match the model, and that I didn’t even know what exactly was wrong with the frame. I didn’t want to rely on the model and moved forward with trial-and-error. I printed several parts to hold the eyepiece, with different eyepiece locations: The part in the photo was a total disaster. It needed quite a lot of filament, at the same didn’t have enough surface area to be glued to the frame, and not enough surface area to hold the eyepiece firmly. The next iteration was a lot better: This part has a lot more surface area, and needs less filament to be printed. I intentionally printed the hole for the eyepiece too small, and had to sandpaper it a little bit, to make the eyepiece stay firmly fixed. Adjusting the focus is done by sliding the eyepiece up and down until the Sun becomes a circle with well defined borders. Part 7: Dust All optical parts should be kept clean. Dust on the mirrors and the lens will make the image darker. Dust on the eyepiece will show up as artifacts on the projected image. Unlike sunspots, the artifacts will not move with the Sun. To clean the eyepiece I used compressed air. To clean the mirrors I used isopropyl alcohol. Part 8: Fire safety Don’t leave devices with magnifying lenses lying around. Once the Sun happened to be in such a spot that its light went right through the lens, burning through the cap of the eyepiece. Luckily, nobody was hurt and no other damage was done. Part 9: Future work Build quality of the base is very poor. The frame tilts sideways when adjusting its altitude despite all my efforts. I’d like to build a new base, but leave all the work to the machines. I already have a model for an X-Carve to make both base parts, compatible with my current frame: A notch along the edge of the half-circle should eliminate the tilt. The precision of the machining should make the base very stable. Maybe next year, when sunspots become a common daily sight, I’ll get to this project. Thank you for reading this far! I hope you enjoyed it.
  2. Hi, I have a Celestron 130EQ and have been told it has a spherical mirror, so wondering if I would get better images if I upgraded it to a (say) SW 130P mirror. And the other important question is will it fit into it.
  3. Hey guys.Its kronos here, and i m here with my Celestron firstscope.As you know ,its quite small with a focal lenght of 300mm.That means i can clean the mirros without unscrewing anything.What can i use to clean them that i can find in my house?Also can i use babywipes to clean them?
  4. Heyyy its me again! Today me and my friend went out to observe! We spotted the moon and focused on it,took some okay pictures with my phone without an adapter( that means having to hold up my phone over the eyepiece 's tiny hole). Then we tried moving towards mars, relatively close to the moon. It wanst a dot but like a small circle with some colour, afterwards we moved towards stars,but instead of seeing these circles with the secondary s reflection in the middle, we saw small circles (like mars but smaller) they were green blue and red coloured i didn't think much of it but then i checked the mirror. And i saw some dust.... Pics bellow.Is it the mirror or is this normal? Also if its the mirror, how do i clean it without removing it, i have a celestron firstscope btw. Thanks.
  5. I have a pair of 15x70 binoculars but due to neck problems I am struggling to use them even when tripod mounted. I am thinking of making a mirror mount but I don't know if they are any good? Can someone please advise me on which mirror I need, size and thickness, fixing method etc.? Do they suffer from dew problems in the UK and if so is there an effective way around this? If anyone could advise me on this it will be very much appreciated. Thanks
  6. From purely visual & practical angles, are there any disadvantages or advantages between F4 or less, to F6 or more, in a Newtonian? F4 (or less) means shorter focal length so shorter tube but lower magnification. But what other pros & cons are there? Quite a few scopes between F4 & F5, maybe the most F5 up to F6 seems to be 2nd most common. What advice for buyers can be given from experience on best F ratio for 6, 8, 10 & 12 inch apertures in respect of optics features, maintenance & scope dynamics? (My first Newtonian 8 inch was F8 - too long. Second 12 inch was just under F5 - only just portable. Current is 10 inch F5 - lighter but I miss the 12's solidity if not bulk).
  7. I have just got a second hand Astromaster 130EQ. I want to say that i have collimated scopes before without the use of a laser but in this case i have 2 questions as this is so far out i cant see what i am looking at half the time. So hopefully you can help, thank you. Info about the first problem: The secondary mirror fixing screw that hold the mirror and the collimation allen key bolts were so loose the secondary mirror had rolled facing the bottom of the OTE. In every other case the holding screw never needed touching and all i had to do were make small adjustments with an allen key, no screwdriver was needed. So this case is a whole different scale then any other collimation i have ever needed to do. You probably all know that i need to get the center of the eyepiece in line with the center of the mirror before can move on with this step. Question 1 What is the best way to do this, shall i just eye it for now? (i have seen people measuring to the center of the eyepiece and then do the same with mirror but then i still dont know if the mirror is facing me directly.) Info about the second problem Every other time i have collimated a scope the mirror and scope were very low quality and just used for practice basically. The old scopes were used to see if i wanted to go further into this hobby which i definitely do. Any how the old scopes had a flat mirror and i could find the center by placing the mirror on paper and tracing a circle template. The thing is this mirror is concaved so any template iswill have to be pushed into the vurve (i think). Question 2 So how can i center the mirror without placing it face down on a piece of paper which cant be a good thing? Thank you. I hope i have not gone on to much, thank you for your patience in reading a long winded post.
  8. Hi everyone. So I'm interested in grinding my first mirror and building my first telescope. I've been reading all that I can about telescopes and watching videos on YouTube. What I want to make is what would probably be best described as a Nasmyth Cassegrain style telescope. My initial idea is to use a 12 inch parabolic primary ground to a focal ratio of 15 and a flat secondary. With a 15 foot focal length the end result will be approximately a 9 foot tube, which is fine, that's actually what I want. I don't care that it won't fit in the trunk of my car, it's not an issue. After reading some articles I've learned that most Cassegrain style telescopes use a convex secondary and a steeper curvature on the primary. Would this be better? Would aberrations be worse with a flat secondary? I want as sharp of an image as I can get without sacrificing either aperture or focal length. It seems intuitive to me that a faster primary would result in a poorer image than using an f15 with a flat secondary...thoughts?
  9. Hello All! Currently, I have a Meade ETX 90 telescope. I really like it and get great views of the moon and planets out of it. However, I am hoping to upgrade to a large reflector. I am looking at various scopes ranging from the Orion SkyQuest XT8 to the forbiddingly pricey Orion SkyQuest XT12i Intelliscope. I know that aperture is one of the most important things to consider in a telescope, but I also realize that people can get "aperture fever" and go for scopes that are unnecessarily large. I am wondering; Is a bigger aperture worth the price jump from 8'' to 10'' or from 10'' to 12''? How much more will I be able to see? I have heard that the best telescope for a person is dependent on the kinds of things they want to observe. I don't really look at deep sky objects (though I am getting increasingly interested in them), and mostly enjoy the moon, planets, and a few double stars. I want a telescope that will accommodate this, but is also able to have a great grasp on deep sky objects. Honestly I think I am on the right track with the scopes I am looking at, but I really want some advice on which size is best for me. What do you think? Thanks for the advice!
  10. Hello, Am very new to this so apologies right from the start. I have recently just bought a skywatcher akyliner dobsonian 200p and i set it up. However the image is very blurry even when i remove all magnification and just look into the primary mirror eveything looks very blurry including the moon or nearby trees etc. I am unsure what the issue could be as i am eager to get started on my stargazing! Could someone please assist me or at the very least point me in the right direction. Kind regards
  11. A very nice condition TAL 1.25" mirror diagonal. Optically and cosmetically in excellent condition, just don't use it any more. £25 plus postage via PayPal fees paid or bank transfer. Stu
  12. Next up on the brown carpet..... ?? A very nice, Baader Maxbright T2 mirror diagonal in excellent condition, just a little dust on the mirror. This has 99% reflectivity, Sitall glass with 1/10th lambda surface accuracy. Male T2 connection one side and Female the other, both with original screw-on caps. Looking for £125 posted or £120 picked up at SGL11. Paypal fees paid or bank transfer please. Cheers, Stu
  13. This is a somewhat custom built, but very nice Denkmeier PowerSwitch. The original William optics diagonal was not in good shape when I received it, so I have replaced it with a nice Baader Maxbright Mirror diagonal, 1/10th wave lambda surface quality, T2 fittings either end. It also has a T2 quick changer fitted to allow correct positioning of the PowerSwitch. Everything is in very good to excellent condition, the diagonal just has some minor dust on it but is otherwise in excellent condition. The PowerSwitch allow you to use straight through, multiplied or reduced views with the slide of a lever, very simple, although clearly you need to refocus each time. Total cost of the components in this is rather high, probably approaching £400 or more! This would be very handy for binoviewers in SCTs or fracs with good back focus. The T2 diagonal has a nice short light path with a clear aperture of 35mm so most 2" eyepieces can be used with no noticeable vignetting. I use a 31mm Nag in these diagonala without problem. It is also handy for solar viewing with a full frontal filter, or potentially a Quark to give variable magnification, back focus allowing of course. Looking for £195 ono plus P&P via PayPal fees paid or bank transfer. I will put this on ABS too in the near future. Cheers, Stu
  14. I've just acquired a rather tired but fundamentally intact Fullerscopes 6" F8 reflector with MK.111 mount. This appears to be an earlier example, supplied with optics by Brunnings of Holborn - the mirror is marked on the reverse, though much of the writing has faded. Although the existing coatings are shot, I shall probably send this away to Galvoptics. but wanted to get see if anyone can shed some more light on the history and probably quality. Not sure if this is plate glass or pyrex, it appears neutrally coloured with no obvious tint - there are a few chips on the back rim at 3 o'clock which might testify to brittleness. The white rectangular sticker appears to be written in ball pen, with something like 'MD / 49' on the top line and perhaps Kirkwood on the bottom line. There are no visible marks on the flat/secondary. I might try a UV lamp to see if I can tease out any more detail from the worn text.
  15. Hi, new here so don't know if this is right place for this question. Can anyone suggest where to obtain a long focus 6" spherical mirror f12 ( minimum f10 ) preferred? Thanks, Robert H
  16. Hi friends, I'd like to make this sunspotter device for my personal use. It seems that I need to buy the following components: - Achromatic lens, 60mm, focal distance 700mm - Mirror 50mm x 50mm - 2 Mirrors 25mm x 25mm But I can't find any website selling any of those . I've seen lots of parabolic mirrors being sold in sizes >= 6'', I've seen tiny achromatic lenses, or lenses costing a fortune. Any advice on where to get lenses and mirrors is appreciated. I haven't looked for the plywood yet, but getting it should be easy
  17. I have had my Tal 2M 6 inch newtonian since 1998 and the mirrors have just about had it. (main has a scratch and foxing) I use my Skywatcher 127 mak/cass at the moment but I would like to get the old Tal back in commission because of the field of view aspect. 6 inch newts have come down in price these years and I was wondering would it be cheaper to buy another 6 newtonian or get the mirrors recoated.
  18. Hey guys A guy in my area is selling a 13.1" Coulter Odyssey, the 2 mirrors. I'd want to get an idea on the optical quality of them. He bought the many many years ago, and they still in the original package, hasn't been used. 1. Would the optics degrade over time if they were wrapped up? 2. What is the general quality of the mirrors. I have heard the optics can vary alot, and they generally not that great for planetary views. 3. He is selling them (and he mentioned the Rocker once) for around $350, is this good for a un-used mirror. I'd like to build a really nice DSO / Planetary Dob, and this gives me hope if the optics are really good. Any advice, tips etc would be greatly appreciated. Tx guys
  19. Howdy folks Whats the best way to clean a mirror, specifically what i think might be tiny metal flecks without causing scratches ? there arent many and it doesnt affect visual use, but i'm tihnking it might affect taking pictures with it and leaving them in place while moving the scope might cause problems too as they will no doubt move from the vibrations of just moving the scope from one place to another is it doable? or best to leave them where they are ?
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