Ricochet

5 hours ago, wookie1965 said:

No it was two distinct moons very close like a 1.5° split double star they rotated as I focused in and out I have never seen this ever. 

When you say rotate, did they gradually rotate as you changed focus, or did they jump from one position to another as you moved through the focus point? I think any issue with your mirrors would have to jump from one point to another. 

18 minutes ago, John said:

Edit: I can see that @Ricochet is having similar thoughts !

Yes! I’ve looked through countless CN threads trying to find out how to collimate this model and all I can gather is that this is the first time anyone has used something other than a laser to check the collimation. 

8 hours ago, dweller25 said:

Here is an image of the secondary support in the ES Dob, it’s not standard !

No, not standard at all. It does look like there really is no way to move the secondary towards the primary to centre it under the focuser. It looks like the secondary is oversized so there might be enough tilt adjustment to get all of the primary in view. 

What exactly do you mean by “double stars”? Do you mean that you get a double image of each star/moon as in two points?

Alternatively, do you mean that each star/moon  looks like an oval? When you change from outside focus to inside focus is the direction of the oval rotated by 90 degrees? If so this is astigmatism and there are several possibilities for the cause. 
 

1. Your eyes. When you observe using large exit pupils the aberrations in your own eye are the dominant factor. Try changing eyepieces to a lower exit pupil and see if the problem disappears once you go below a certain exit pupil.
2. The eyepiece(s). Many eyepieces have some level of astigmatism, particularly towards the edges. Centre the object in the view and see if it improves and try different eyepieces of similar focal lengths to see if it makes a difference. 
3. The mirrors. It is possible, but unlikely, that one or both of your mirrors have some level of latent astigmatism. However, many mirrors that are perfectly fine at ambient temperature will become astigmatic whilst they are cooling. Given that the cooling time was only ten minutes with a fan blowing onto the mirror then I think it is highly likely that this is the culprit. The solution is to allow the scope more time to acclimatise before observing. 

Does your secondary stalk look like this? 

If it does you have all of the normal secondary adjustment options. 

The offset refers to how the mirror is glued to the stalk. You do not need to think about it to collimate the secondary. All it means is that you only have to check that the central bolt is centred in the tube to start collimation. 

When you look through the focuser the secondary should appear to be round and circular. 

Once you get to collimating the primary the shadow of the secondary will appear to be offset but you don't need to worry about that yet. 

You also need to put some paper or card between the secondary and primary while you are doing this first step so that the reflections from the primary do not confuse the issue. You have placed the green circle in your image around the reflection of the primary, not the edge of your secondary. 

I bought enough of these in various thicknesses to make a stack so that the base was just floating off the Teflon pads and then tightened the central nut to pull it back down and get the required friction. I think I probably went for the maximum 80mm outer diameter and then a central hole to match the size of the connecting bolt. 

Teflon/PTFE disc

5 hours ago, Neil H said:

Hi well I tried it and could not focus ? , I popped in a extension then you could just make out a Sun spot but still would not focus , I know it was not bad seeing as my HA telescope was focused ok , so do I need more extensions ?

 The focus point for the sun should be almost the same as for the moon etc. The only difference in the optical chain is the filter and I wouldn’t have thought it would make that much difference. Have you tried the filter with other scopes? How much did the focus point move with those?

On 09/10/2023 at 13:58, Planetarian said:

Since you've flocked the tube, have you noticed lint from the flocking paper being collected on the mirror surfaces? I'm planning to flock mine, but a bit worried about residue.

Before you fit the flocking paper run a sticky lint roller over it to pick off any loose fibres. If you don't have a roller you can make a loop of sellotape with the sticky side on outside, and large enough to go around a few fingers, then roll it over the flocking. 

13 hours ago, Coolhand1988 said:

I like the adjustable eyecups, unsure if that is a unique design for these eyepieces?

 

The "look" of them is a Vixen deisgn, and the NLV Plossl range have something very similar. Other eyepieces with twist up eyecups are the BST Starguiders, Pentax XWs, UWANs/Old Nirvanas, Old Meade 5000 SWA/ES Maxvision and probably more that I've forgotten. Televue Delos/Delite have adjustable eyecups via outer barrel sections that slide up and down and are secured at the desired height with a lock ring. 

On 07/10/2023 at 09:54, Bugdozer said:

Is it better to put the filter directly in front of the Barlow?

As a general rule, it is always better to place the filter that reflects the most light as far forward in the optical chain as possible. Any light reflected of a component (in this case the UHC filter) could then be reflected back off an element in front of it (e.g. the lenses in the barlow) causing unwanted reflections. Some cheaper UHC filters also have issues caused by non-uniformity of the coatings. However, if you have any optical issue, and that issue moves in line with any component, in this case your eye, then it is usually the case that the issue lies within the component that you have moved.

From a quick look at your posts I see references to an F10 SCT and a 25mm eyepiece. Assuming that you were using these two items then you will have had an exit pupil of 2.5mm, which is about the smallest size that you want to use with a UHC filter, because the amount of light blocked by the UHC filter has to be counteracted by increasing the exit pupil to achieve a bright image. If you then add in a 2X barlow you will be decreasing the exit pupil to 1.25mm, which usually makes extended objects too dim even without a filter. With the additional light loss from the filter, the entire view will be so dim that my suspicion is that your brain doesn't have enough information to properly filter out the artefacts that it automatically removes under brighter conditions. Specifically, I would suggest that you may be seeing the blood vessels in the retina, which are in front of the photo-receptive cells, but are absent from the central region.

24 minutes ago, Coolhand1988 said:

Referring to post 3 of this thread?  With my eye floaters, a 4mm EP in an F8 scope is the smallest FL to ( hopefully ) view comfortable with an exit pupil of 0.5mm?

Floaters do not depend on eyepiece focal length but on exit pupil. A 4mm eyepiece will tend to show floaters because it is unusual to have a scope with a focal ratio less than f4 so the exit pupil will tend to be 1mm or less. When floaters become a problem will vary from person to person (eye to eye even) so you will need to find when they become problematic for you by experimentation. Floaters are usually only a problem with bright objects, so lunar and planetary, and a 0.5mm exit pupil will tend to be too much for these objects. 

18 hours ago, Lurcher said:

So sorry for not replying to your question before! You're probably past caring now! Lol. I want to change it for a larger 9 x 50 finderscope which I'm more used to using.  (The StellaLyra comes with an 8 x 50). Sorry I didn't reply sooner! All the best!

I believe the 8x50 and 9x50 finders are exactly the same model. Some vendors advertise them as 8x and some as 9x for an unknown reason. 

13 hours ago, sojourneyer said:

I am seeking a mount/tripod with limited vibration, and in this regard the tall riser on the Pronto worries me.

It would not be the “riser” that worries me, but the telescope over pivot arrangement and prior reports on the performance of the mount head. If you’re after a Skywatcher alt/az then the AZ4 and AZ5 are the mounts I would be looking at.

52 minutes ago, Moonshed said:

Yes, it will definitely be a refractor and probably a Skywatcher, maybe 70mm on a simple Alt-az mount. The Skywatcher Mercury 705 AZ3  comes in at £155 on an alt-az mount, seems a good solution.

Given the bias towards lunar and planetary, the Skywatcher Mercury 707 might be a better choice. The slower focal ratio should reduce chromatic and spherical aberrations, which will mean better performance. The downside is that the mount doesn’t look as good as the AZ3 that is supplied with the shorter scope.

35 minutes ago, Moonshed said:

Now that I have finally decided what I am going to do, buy a 70mm refractor, all I have to do is sell my gear. That’s the 8” Celestron (circa 1985 but in great condition) the Bresser Exos 2 GOTO mount, Zwo camera, PoleMaster, flipmirror etc. All I intend to keep is the Canon camera, for “normal” use, and my case of EPs and filters that I can use on my new scope.

I will get busy pricing things up, not an easy job. I would love to sell the lot to one buyer at a discount but that’s very unlikely so it’s going to be a lot of bits and pieces unfortunately. It has to all go though and will not only pay for my new scope but supply some much needed extra cash as well.

When ready I will advertise it here. Are there any other good sites I could place it?

Cheers

Keith

https://www.astrobuysell.com/uk/index.php is a good place to sell your old equipment in addition to these forums. However, I would be inclined to keep hold of it for a while in case the new smaller scope reignites your enthusiasm enough that you want to start using your old equipment again.

7 minutes ago, Moonshed said:

I will be observing the moon, planets and comets, not to bothered about DSOs.

In that case I would definitely go for an ED refractor.

17 hours ago, niallk said:

A Cheshire can be used to collimate the primary - a concenter cannot.

Can you not align the primary doughnut with the more central rings then?

Do you want to do planetary and lunar observing with the scope? If so an ED refractor is the way to go. If it isn’t important and you’re more interested in DSOs then the extra light grasp of a short 4” achromat or 5” Newtonian might be a better choice than a 3” ED.

1 hour ago, a6400 said:

I have heard of Barlowed (any barlow) laser collimation and that the laser doesn’t have to be itself collimated.

Is that an option?

Yes, for primary collimation. For collimation in the dark I would suggest leaving the secondary and just doing the primary. You could use a normal laser method you half do the secondary but if you've collimated in the light the secondary should be much less prone to movement than the larger primary. 

12 hours ago, John said:

The reason that I'm wary of being able to help, apart from lacking the time, is that I don't know the ES design

Reading through a previously linked thread it looks like it might be held in place by some sort of sling system with screws that are extremely fiddly to reinsert.

24 minutes ago, Mandy D said:

The correct spelling, at least in the UK, is centre.

I don’t think the name is derived from centre, but from concentric, with a standard -er suffix, as in a tool that makes the mirrors appear concentric, so Concenter is correct. Additionally, as it is a name, the spelling given by the manufacturer is correct in all countries. I certainly don’t change the spelling of my name if I cross the border from one country to another. 

20 minutes ago, lawsio said:

one of which is a 40mm and using the online calculator it looks like it gives me near as dammit the same FOV as the 2" SL UFF 30mm

I think there must be something wrong with the online tool you have used. You can't get a wider true field of view from a 1.25" eyepiece than with a 32mm/50° Plossl. As a result the 40mm Plossls have a more restricted apparent field of view, about 40°. The online tool probably had the 40mm listed at 50° like the rest of the line. 

Congratulations on the new scope purchase. 

You never align the spider with the crosshair. You align the secondary using the circular edge of the Cheshire/sight tube as a guide, and then align the doughnut of the primary with the crosshair. 

I was in a similar position. I had an 8” Dob, but wanted a small refractor for grab and go. I went for the 72ED, so a slightly shorter focal length (420 vs 500mm) and I have found that I don’t really use my 2” eyepieces and diagonal with the scope and instead take just a 1.25” diagonal and three 1.25” eyepieces for grab and go sessions. A 24mm 68º eyepiece gives a wide enough field for most nights. It is only if I specifically want to have the widest possible views that I would take a wider eyepiece. With this in mind you might find that you are better off buying just the scope for now and trying it with your existing 1.25” eyepieces to see if you feel the need to buy any 2” eyepieces to go with it. That would also allow you to assess the exit pupil and darkness of the background sky at various focal lengths before committing to a 2” eyepiece in that focal length.

Having said that, I don’t think that 1.25” eyepieces go wide enough for a finder eyepiece to use with your Dob, so you probably want a 2” eyepiece or two for that scope whether or not you use them with the grab and go scope.

There is also the new ES Reflexsight finder which looks to be a small Telrad with a standard Vixen/Synta finder foot.

I owned a Hotech for a short time and unfortunately I found that the self centring mechanism did not work reliably, either with the laser in the adaptor or with the adapter in the focuser. I could tighten the mechanism and have the laser pointing at a certain point, but if I simply loosened and retightened the laser or adapter the laser would be pointing at a completely different point, making it impossible to collimate the telescope. Given that both the laser and the adapter had the exact same fault my conclusion was that the fault lies in the design of the mechanism.

The solution was to use the Hotech in a 1.25”-2” clicklock adapter in a 2” clicklock focuser and to use the clicklock clamps instead of the system built into the laser. However, there may also be an issue with using the 1.25”-2” clicklock in your existing 2” focuser. The adapter has an undercut and if your 2” focuser has a low profile eyepiece clamp then you may find that the clicklock (or any eyepiece with an undercut) can be tilted in the focuser, which again throws off the collimation.

My preferred tools for collimation are the FLO premium Cheshire for the secondary, and a collimation cap for the primary. If you want a laser so you can see the collimation change as you adjust the primary then using the barlowed laser method is a much more accurate (and cheaper) option.