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Ricochet

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Posts posted by Ricochet

  1. Is it coma you are seeing? Perhaps the focuser is sagging a bit under the weight of an eyepiece which would miscollimate the telescope and shift the coma free zone from the centre of the FoV. Coma appears to "point" towards the centre so moving a star around the FoV will reveal where it points to. If it is not the centre try comparing different weight/size eyepieces and see if the position changes according to eyepiece size.

    If the star image appears to be an oval one side of focus and a perpendicular oval the other side of focus then you could have astigmatism present. As the Heritage focuser rotates you will also need to loosen the eyepiece clamp and rotate the eyepiece to rule out it being inherent in the eyepiece you are testing, and rotate your head to check whether it is inside your eye (more likely at larger exit pupil, see the Televue chart below). If it is a function of your telescope mirrors check multiple times during a session, it could be induced only while the scope is still cooling.

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    If the stars appear slightly triangular then you have pinched optics, and usually overtightened mirror clips on the primary are to blame.

    However, with just a collimation cap being used so far, I suspect the collimation needs to be looked at in the first instance with a decent cheshire or concenter.

     

    • Like 1
  2. The problem here is trying to compare eyepieces in "hazy" skies. The whole experiment is atmosphere limited and so no real comparison can be made. The field being brighter reveals that the SLV must have higher transmission, but why is the field bright? Because of light from the moon scattering in the atmosphere. Repeat the test in good clear skies and I am sure that the SLV will have a darker background sky with brighter objects because the coatings and baffling are far superior. Coma will be approximately the same in both eyepieces because it is primarily caused by the parabolic mirror of the telescope rather than the eyepiece. Astigmatism, field curvature and chromatic aberration are probably going to be the eyepiece aberrations to look for.

  3. On 06/01/2022 at 00:17, biggsthebeast said:

    @Budgie1 just visual, I would basically like to set it up in my bedroom and just look out or even take it to a mountain local to me 

    Have you got an outdoor area to observe from? Looking out of a window will degrade the views through the telescope and restrict the area of sky you can see. 

    When you go to the mountain how will you get it there and how far will you need to carry it once you get there? 

    Something from the Skywatcher AZ Pronto range is probably going to be the most suited for your scenario and budget. 

    • Like 1
  4. On 04/01/2022 at 10:26, Joacim said:

    Is it really worth getting a 2", the Astronomik UHC 2" is almost double the price for the 1,25"?

    Yes. In my experience/opinion you will want a wider field of view with an 8" dob than you can get from any 1.25" eyepiece. If you have a 1.25"-2" adaptor that is threaded for filters you can use a 2" filter with 1.25" and 2" filters. If you buy a 1.25" filter, you will end up also having to buy the 2" filter later. 

    The 24mm ES68 is a nice eyepiece, but in line with my comment above, I would also look at the 28mm or 35mm in that range. With your skies the exit pupil with either should be ok. For comparison my widest field is a 28mm 82° eyepiece. 

    • Like 1
  5. 2 hours ago, MichaelMcD said:

    @Ricochet who looks like he/she has the same telescope as me

    I've got the 8" dob so not quite the same, but from the same manufacturer and series so some parts are the same or a similar design. 

    1. All telescopes natively give an inverted image. Those with a diagonal may modify the inversion further, but for astronomical viewing it doesn't matter which way is up. 

    2. You can use the coordinates with a go to mount, but for manual mounts the dials are too small and too imprecise to be useful. Learning the constellations and star hopping is the way to find an object manually. 

    3. If you mean a nebula, then yes you will see this if you are looking in the right place, unless you are right in the centre of a city in which it could be possible to have enough light pollution for even Orion to be obscured. The 25mm eyepiece will be the correct one to use for this object. The nebula is actually visible as a naked eye object, and appears as the middle star in Orion's sword. If you have aligned your finder correctly this should make it fairly easy to find. 

    If you mean the actual milky way then no, I can't see it from my home, but from dark sky locations it is visible to the naked eye. 

    2 hours ago, MichaelMcD said:

    what I seemed to capture this evening which was "just" pinhead-sized dots. 

    All stars (except the sun) are so far away that they will only ever be a point of light in any telescope you can buy. 

    2 hours ago, MichaelMcD said:

    From the balcony I have the Plough directly in front of me and what I believe would be Saturn behind some buildings at about the 8 o'clock position as I stare open-mouthed at the Plough.  Will be interesting to see how well I can capture that or Jupiter if I can get access to them in the coming weeks (if that's even how the universe works).    

    Ursa major is in the north east and Jupiter and Saturn are in the south west so I would think you will need to be on a rooftop balcony with a full view of the sky to be able to see both. The two planets are quite low now, and from my location Saturn is setting by about 18:30. 

    • Thanks 1
  6. 13 hours ago, Shimonu said:

    Fantastic help, I feel like I understand the steps of collimation better now and it certainly doesn't feel as daunting.

    I always put my equipment in the car and go just 5-10 minutes away. Is it crazy to think the collimation would hold if done at home and then going out for a night?

    If you do the collimation/locking screws up tightly enough then it might be fine. In any event you can easily check once you get to your site using either the barlowed laser method or by shining a red light torch into the side of a cheshire. Once on site I would only ever adjust the primary.

    • Like 1
  7. 27 minutes ago, JP-S said:

    |If these 2 conditions are met then that's it for secondary mirror positioning, correct?

    No. After you have the secondary centred, you must adjust the tilt so that the cross hairs at the bottom of your cheshire intersect with the doughnut in the centre of the primary mirror.

    Once that is done, you can collimate the primary using a collimation cap. You adjust the primary so that the dark hole in the centre of the cap appears to be in the centre of the doughnut.

    32 minutes ago, JP-S said:

    Tracing lines suggests the vertical vanes are off:

    Is this something to worry about?

    No. It will make almost no difference aside from slightly modifying the diffraction spikes on bright stars. It is far more important to have the mirrors in the right place. The vane in question is the right hand horizontal one that appears thicker. If this is because the vane itself is twisted you can attempt to straighten it. If this is because you have a wire fixed to that vane for a secondary heater the only improvement would be a thinner wire.

  8. 21 hours ago, JP-S said:

    I've added coloured circles for reference. Do I want to center the red circle inside the yellow circle? Or the blue circle inside the green

    Everything you have marked should be concentric. The only thing that is not concentric is the shadow of the secondary mirror, which is the dark shadow outside of the red circle, which will be offset towards the primary mirror. 

    21 hours ago, JP-S said:

    My cheshire/sight tube doesn't quite let me see the whole mirror

    Try extending the focuser and/or pulling the cheshire out of the focuser until you can see the whole secondary, if it is one like the red FLO premium cheshire that can be clamped at any point along its length. 

    • Like 1
  9. The secondary needs to move "down" in your picture. You want the gap between the edge of the focuser tube and the secondary mirror to be the same all the way around. If you have a sight tube (included in long cheshires) or concenter you can more easily see where the secondary needs to be using either the edge of the sight tube or a ring with the concenter. 

  10. 8 hours ago, cajen2 said:

    Nobody has told me, but is the Williams Optics version exactly the same as the APM?

    I think the problem is that we need someone to test them side by side to determine if there is any difference in reality. The design of the lenses internally is the same but when the APM line was announced it was claimed that the lens coatings are better. Coatings and stray light control make a big difference in performance so if they are better it would be worth paying the extra in my opinion. Are they actually better in practice? I don't know. You should also note that the eyecup has been changed in the APM version, which may make the eyepiece more or less comfortable to use. 

    However, for planetary viewing I personally prefer to use binoviewers. This necessitates using smaller eyepieces so that you can comfortably get both eyes positioned over the eye lenses. Usually you will need a barlow or gpc to be able to bring the focus point within the range of your focuser travel, which means that long focal length pairs of eyepieces that aren't necessarily well corrected at your telescope's focal ratio will actually be fine. Sticking with the APM brand, the UFF range (60°-65°) are often used for this. 

    • Thanks 1
  11. The eyepiece has to be a set distance away from the primary mirror. Because your adaptor adds length to the focuser, you will have to wind the focuser further inwards to "remove" this extra length. So long as your focuser has enough in travel for you to be able to focus your eyepieces, there will be no difference in how you use the focuser compared to using old 0.965" eyepieces.

    • Like 1
  12. 3 hours ago, Space Explorer said:

    on the one mr spock has shown, apparently the 4 black brackets to the top part of the scope can actually be undone and the top part can be securely locked to bottom half, completely enclosing the mirror, has anyone tried that and how did it change your viewing experience? 

    Anyone who tries that will not see anything. The shape of the primary mirror determines the exact position the eyepiece must be at. If you do not extend the truss poles the eyepiece will be in the wrong position and the only thing you will see will be the inside of the telescope. 

    • Like 1
  13. 29 minutes ago, Roog said:

    Do you think that these could work?

    Yes, those would work, but you would probably also want a parfocalling ring so that you can set how far the stack slides into the focuser. However, with the cost of that set there is no real financial advantage in buying it over the M54 rings which will solve focusing with both 1.25" and 2" eyepieces.

  14. 3 hours ago, Roog said:

    The male thread on the 2" Clicklock (part # 2956254), seems to be M54, if i could get a 20mm extension tube with a M54 female thread at one end and a M54 Male thread at the other?

    This is what you need to do, but you may need more than 20mm to bring any 2" eyepieces to focus. 

    FLO sell 8mm and 9mm extension rings. You'd need at least two, but you could email FLO and see if they are able to source any other sizes. 

    The other option would be to see if you can fit a Baader UFC system between draw tube and 2" Clicklock, but this needs careful selection of parts so you end up with the right threads either side of the UFC. 

  15. Yes, you need an extension, preferably one that fits between the focuser drawtube and the 2" clickclock. Which specific 2" Clickclock have you fitted? Also you should measure the height of the part(s) that you have removed from your focuser and compare it to the height of the 2" clicklock that you have fitted.

    As a temporary measure, you could refit the stock Skywatcher 2" eyepiece adaptor parts and put the 2"-1.25" adaptor in that, so that you can have the ease of a clicklock with your 1.25" eyepieces.

    • Like 1
  16. With an f5 dob you're not really missing out on having a 30-40mm eyepiece as the exit pupil (6-8mm) is too large unless you are at a really dark location. What you are missing out on though is a wider field of view. With your scope the eyepieces I would be looking at are the 21mm TV Ethos and the significantly cheaper option of the 20mm APM HDC, assuming that you don't need glasses to observe and can get your eye close enough to the lens. Another option would be an 82° eyepiece at around the 25mm mark. 

  17. 5 hours ago, HollyHound said:

    So…. I’ve gone for it and can’t wait to try out a matched pair very soon 👍

    I tried it and they were a bit too big for me, or rather my nose is too big to fit in the gap with the eye cups raised. What I have thought about since is that the m43 thread could be used to fit Morpheus eyecups and extensions instead, which may give that little bit more room. 

    • Like 3
  18. On 03/12/2021 at 07:02, Stardaze said:

    Do the HR’s still suffer with bloat on planets?

    I was just able to have a quick look at Jupiter through gaps in the cloud. There is no bloat as far as I can see, but I may have overstated the visible detail as I couldn't see any banding tonight, just a bright disk and four moons. 

    • Thanks 1
  19. There are two designs of lens cell for the generic Chinese barlows, with and without filter threads. Brands can order the same barlows with and without the threads, and can even change their choice for different batches. Just because there is a picture of one without threads doesn't mean all of them are unthreaded. I've got two ae barlows and both of them have the cell with filter threads. 

  20. 3 hours ago, johninderby said:

    listed as a 1.6x not 2x

    When screwed to an eyepiece. Extending the light path increases the magnification and my drift time measurements gave a magnification of 2.1x when screwed to the binoviewer nose piece. I expected higher but that's what the timings say. 

    3 hours ago, johninderby said:

    Looks.different as well

    Mine look identical to the photos for the WO barlow, which I assume is specified as 2x when attached to the nose of a binoviewer. 

  21. I use an AE555 I picked up from Astroboot, which gives 2.1X and the nose from the barlow that FLO sell as the Astro Essentials Barlow, which gives 3.1X, but this does generate some reflections off an element inside the binoviewer when the moon (or some of it) is drifting out of the field of view. It wouldn't surprise me if the WO linked above is the same as the AE I have so that would be my choice if I was buying a binoviewer barlow now.

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