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Ricochet

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Everything posted by Ricochet

  1. The only thing you might be missing is the age of the original set of posts in this thread. The attachment must have been deleted at some point.
  2. Congratulations on the new eyepieces. I look forward to your thoughts on the views with the Orion once you get a decent chance to use it. I'm not sure about that eyecup though .
  3. How have you got on recharging those silica gel packs? I bought a couple to try in my cases but the claim that they can easily be recharged in a microwave was quickly disproved.
  4. That isn't right, I can I only imagine that the telescope isn't quite extending all the way for that to happen. As for the telescope being or not being "right" it is probably impossible to tell without looking through it. Trying to find a local astronomy group to get a second opinion is probably your best bet, but I suspect it's probably fine.
  5. If your conservatory is in the sun then the scope could get relatively hot and need longer to cool. I would be inclined to leave it outside at about 45° with the caps off to cool rather than just by the door. With regards to contrast on DSOs you might find there is an advantage to be found by adding a shroud over the open central section. Likewise flocking the inside of the tube and baffling the mirror edge can help control stray light. For planets you might want to invest in a barlow to use with the zoom. You can probably go down to about 5mm if the conditions allow but you are currently limited to 8mm. The extra magnification will make the planets larger although they will never be massive in any scope. Generally you will find it best to observe celestial objects when they are highest in the sky and when the moon is below the horizon. You should also aim to observe over vegetation rather than houses or other structures that will hold onto heat and release it throughout the night.
  6. While you're stripping and flocking make yourself a baffle to block the edge of your mirror. I mounted mine on top of the mirror clips but others have simply laid theirs on the mirror under the clips. Make sure there is a gap between the edge of the baffle and the inside of the tube. Here's a picture of my oversized proof of concept test baffle:
  7. What's the bag you're using? I'm often pondering alternative options to the standard maplins case.
  8. I think it is possible. Consider the simplified diagram of a Newtonian tube below (secondary/spider not shown). Light enters from the top and strikes the primary mirror at the bottom. The red lines signify the parallel light rays from a point at the left hand edge of the field of view and the blue lines those from the right hand edge. At a certain distance of drawtube intrusion it must be possible for some of the light from one side of the field of view to be diffracted by the drawtube but not the light from the other side. However, note that the real angles will be smaller and should not be constrained by the width of the telescope tube. Judging by your first image I'm going to estimate your field of view at about 3° and I'm going to estimate the distance between the primary mirror position and the focuser at 500mm. We can then estimate the "distance" of the edge of field rays compared to the on axis rays when passing the focuser as 500 * tan (3°/2) = 13mm, let's call that half an inch. The distance between the right and left hand edge rays is therefore an inch and the gap between the tube and mirror is also usually in the region of an inch. Based on that we can estimate that: If the focuser intrudes by less than 0.5" it will not affect the image If the focuser intrudes by more than 0.5" but less than 1.5" it will affect part of the image (at 1" it will affect half of the image) If the focuser intrudes by more than 1.5" is will affect the entire image Of course, the question of whether the focuser intrudes into the light path is not necessarily the same as the question of whether it doing so is responsible for the effect that you are seeing. There was a small clear-ish patch of sky last night so as a test I tried varying the amount by which my drawtube intrudes into my Dob. At times I thought that I could see dual spikes but I could never be sure that it was definitely there and not caused by something like a slight unfocusing due to eyepiece field curvature or the like. Perhaps the hazy conditions did not allow a good test, or I would need a camera to test it. As such I would suggest it is worth exhausting every other possibility (i.e. possible focuser/sensor tilt) before cutting into the drawtube.
  9. Possibly, if the diffraction is different to how I was thinking it would be. I was assuming it would act like a thick spider vane and create a spike perpendicular to the drawtube axis, but given the thickness perhaps it acts as three independent edges as shown in the image below where we have the following diffraction causes: Red - Spider vanes Blue - Secondary obstruction Green - Sides of drawtube Yellow - End of drawtube If the drawtube is only just catching the lightpath then possibly we only have the yellow drawtube diffraction spike and not the geeen side spikes, which makes sense in the original image if from the perspective of the camera, the drawtube was on the left.
  10. Don't worry about it. My suggestion can't be right looking at the original image again. Go with the suggestion to check your focuser is aligned properly.
  11. Where is your focuser in relation to that last set of images? Is it at the top? If the focuser is protruding enough to obscure some off axis rays but not enough to obscure on axis rays then it seems to me that you could get an additional diffraction spike on one side of the image. The additional spike would be orientated at 90° to the focuser tube so the additional horizontal spike suggests a vertical intrusion and your test star not only moves left to right but top to bottom.
  12. I wouldn't worry about 0.2 difference in focal ratio. I added a fan to my 8" dob and I am certain that it helps. However, mine is suspended via elastic so that vibrations are not passed through to the scope.
  13. The question here is whether you enjoy those things because that is your interest, or because those things happen to be the strengths of your current telescope. If it really is lunar and planetary that interest you most with a small amount of DSO observation thrown in then aperture is not quite as important and so the 8" or even a Mak/SCT would be good choices. On the other hand if you think you would really like to observe DSOs, but it is just the small aperture of your current scope holding you back, then go for the biggest one that you can easily take out under the stars. An 8" under the stars will show you much more than a 12" in storage because the effort of setting it up prevents you getting it out.
  14. Nice effort, I like the height of the mount. I think I would be inclined to modify the alt bearing to use a pair of tube rings though.
  15. As will be better explained by the article Charic linked, the point of the barlow is not to make the laser more straight, but to diverge the beam, effectively turning the laser into a narrow torch that illuminates the centre spot of the mirror. This means that it doesn't matter if your laser is slightly miscollimated, the focuser doesn't centre it perfectly or if you didn't quite get your secondary position absolutely perfect, because the beam still illuminates the centre spot. Instead of the usual laser method of primary collimation by getting the laser beam to return down the hole it is projected from, which with cheaper lasers might be harder to judge than it should be, you centre the shadow of the centre doughnut on the angled face of the laser (in my case I have a dot in the very centre of my primary as well as the doughnut so the shadow of the dot disappears down the laser hole as an additional check). For your case I would expect that your Hotech laser is of such quality that you can use it in the "normal" method with no issue, but the barlowed laser method allows the use of any any cheap laser and any cheap barlow to achieve the same accuracy. Note that it has to be a barlow, a powermate or telextender won't work because of the difference in how they work.
  16. I suggest using the barlowed laser method for easily collimating the primary without the need to grow longer arms.
  17. If you are having the window fitted solely with the intention of observing through it then neither. No attic window is really suitable for observing through. Windows are not made from optical quality glass and will degrade the image. If you want to open the window for observing then the top hinge ones only open ~45° so you won't be able to really get the glass out of the way. Centre pivot windows probably open further but at best you'll have half of the window aperture to look though and in any case the thermal currents racing through the open window will degrade the views. Taking your telescope outside will always give better views and allow targets to be chosen from a much larger portion of the sky.
  18. That looks to me like something I had with my Newtonian where the dark spikes were not indicative of something causing diffraction in those areas but something blocking it. Try stopping down the aperture and see if the ring of diffraction (with the dark spikes in it) around bright stars is removed.
  19. Proving that sometimes it pays to ask, today I received a package of three items from Baader, two of which they don't usually sell. So from left to right; an M68 Clicklock, an M68x1mm to M68x0.75mm inverter ring and a Morpheus eyepiece holster. The inverter ring is the special piece here because it has allowed me to directly fit the Clicklock to a Bresser Hexafoc focuser and dispense with the low profile 2" clamp that comes as standard and doesn't hold any eyepiece or adapter with an undercut squarely (!!!). And finally a picture of the Clicklock actually fitted to the focuser. It was quite a relief when it went on given that it fitting was dependant on my ability to use callipers correctly.
  20. Plastic!! I'd noticed the 90mm fracs all come with a different focuser but never realised it or the tube clamp was plastic. They really should be putting sturdier parts on the" Messier" product line I think. Do you? When I emailed them with feedback on aspects of their dob design that could be improved the sound of silence was deafening.
  21. It's not a case of a "Skywatcher" bracket and a "Celestron" one, rather that you have the standard Synta bracket and the one pictured above is unique to the Astromaster range. The RDFs look identical because they are identical. Anyway, the red dot always points to the centre of the finder window. If you see it anywhere else then your head must be in the wrong place. When you turn the adjustment knobs the entire finder moves up/down/left/right, not the red dot. With regards to the optical finder only just having enough movement "vertically" the standard thing that people do is to place a shim under the finder shoe to angle it a bit. If it needs to be raised at the back loosen off the screws/nuts holding the shoe to the tube, push your shim in from behind (a piece of card will probably do) and then tighten up the screws/nuts again. You have to be careful doing this of course because the nuts are not captive and there is the risk that they fall off and you might need to use a tool on the inside of the tube (near your secondary!) to do the nuts back up again. The other cause could be that your secondary mirror is not quite centred properly. If so then the primary will be tilted to compensate and the optical axis of the telescope will not coincide with the mechanical axis of the tube. In other words, check your collimation before you try adjusting the finder bracket.
  22. Good job. The Astromaster series used to have a custom RDF that didn't get great reviews so it looks like they've made a change to fit a standard RDF instead. Shame that the new Celestron bracket isn't quite right, perhaps you should forward what you have had to do to Celestron so that they can make further adjustments for the next batch.
  23. If the finder isn't physically moving between your daytime alignment and the night time use it must be that whatever objects you are using to align it are not far enough away to remove the parallax effect. What I do is to use the daytime alignment only as a rough guide to get the telescope onto an obvious astronomical target (say the edge of the moon) and use that to tweak before using Polaris for the final alignment. Polaris is the best object for alignment because it won't move in the time it takes to get everything aligned. If you do get the 80mm Startravel I wouldn't worry about it only having a red dot finder. My preference is to have both a red dot finder and a 9x50 RACI finder. The RDF makes it easy to point the telescope at a certain patch of sky and then the RACI can be used for star hopping. The RACI finder has a field of view of about 5.5° but if you get an eyepiece that maximises the field of view for a 1.25" barrel (18mm 82°, 24mm 68°, 32mm 50°) you will have a field of view of 4°, which will make the Startravel suitable for use as a finder in itself. Given that you are concerned about the size and weight of the telescope I think it would be a good idea of you were to visit an Astro retailer where you could actually handle some telescopes before purchase. @FLO First Light Optics, the sponsors of this forum, operate from a warehouse in Exeter that you can visit if you contact them in advance and I am sure that they would be able to help you to find your ideal telescope and also give you some pointers on where you can take it to avoid those city centre lights.
  24. What telescope do you currently have? Aligning the finder scope and telescope is a pretty basic requirement to be able to find things. Was it a red dot or a straight through magnifying finder with a reversed image? Perhaps we can help advise with that. A dedicated astronomy scope on a proper az mount will be a better choice than a spotting scope for astronomy. Even if you were to use a spotting scope I would still suggest an astronomical az mount over a photo tripod so I would suggest starting with a new mount and going from there.
  25. Yes, but only one of them has the eyecup set at the right height.
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