John

8 hours ago, tooth_dr said:

This is a great thread but it really needs photos of all these brilliant suggestions 

Here are photos of the finders on my 12 inch dobsonian and of my Sky & Telescope Pocket Sky Atlas along with another very useful tool. Hope that helps

Hi and welcome to the forum.

Unless the collimation is massively out, you should at least be able to get the scope to focus. You can fine tune the collimation once you have cracked that.

Orion Optics scopes usually need an extension tube of around 50mm to get eyepieces to focus - do you have one of those fitted ?

19 minutes ago, Osiris777 said:

Looks aside.. do you think a telrad is going to be too much for a small refractor? (WO Z73)

I think the Telrad would work OK but would be a large addition to the WO 73. Here is a Telrad on an ST80 refractor:

Hi and welcome to the forum.

We need to know more about the scope (eg: the specifications) that you are going to put on the mount, whether you have a budget in mind and whether you are interested in imaging, visual observing or both  

This website does actually sell parts of scopes including the top piece you pictured and more besides:

https://www.astroboot.co.uk/AstroBoot

They are based in Europe though and I've no idea if they will ship to the USA. You would need to work out what suited your purpose and how to actually make the modifications to your scope - the supplier would not take any responsibility for that.

Travel for me. Got all the kit and more that I'll ever need

Can I have 6 months please if it's just my other half and I ?

1 hour ago, wastedyears1981 said:

...How accurate the parameters against 'real-life' (obviously light pollution and weather permitting) ?

If you get the settings right, the depiction of the size of the field of view will be accurate but as for the visibility or other wise of the object itself, I would take that with a very large pinch of salt.

Observing conditions, observer experience and equipment make a really big difference to what is actually seen "at the eyepiece".

I've just looked at Stellarium and zoomed in on Orion using the parameters of one of my scopes and eyepieces. It shows a couple of nebulae there (the Flame Nebula and the Horsehead Nebula) rather clearly but the reality is that these objects are really, really difficult to see even for experienced observers under dark skies with big scopes.

So the size of the view can be accurate but not necessarily it's contents !

I use a Skywatcher 6x30 RACI finder on my FC100-DL. It fits neatly into the Takahashi 30mm finder clamp.

The trick is to find a finder mount that will fit your finder and also can be fitted to the 2 holes on the Takahashi FC100. This is the Takahashi 50mm finder mount, it might fit your 50mm Orion guide scope ?:

https://www.rothervalleyoptics.co.uk/takahashi-finderscope-bracket-for-7-x-50-finder.html

I use a Skytee II and a Giro Ercole for my 100mm - 120mm refractors. My 130mm refractor needs something more stable again to get the best from it. I managed to get a T-Rex for that which has a similar capacity to the Rowan AZ100 but is out of production now.

The Ercole and the Skytee II are around the same capability but the Ercole is a better made and finished product. The Skytee II has slow motion controls though which can be very useful.

Difficult to knock the capability of the Skytee II for what it costs. The dovetail clamps do need to be upgraded though which should be factored into the price.

This is a 12 inch. It's an Orion Optics tube and the whole thing weighs about as much as a Skywatcher 10 inch dob. I did have a Meade Lightbridge 12 inch dob and that was much heavier so didn't get anywhere near so much use. Best scope I've ever owned in terms of what it has shown me

2 hours ago, RobertI said:

Agreed about the zoom. You wouldn’t think that a cheap zoom with an achromatic barlow would be that good for doubles, but it seems fine.....

It's a good combination for planets as well:

If it is a .965 inch diagonal your choices will be very limited I fear. Check that first. If the scope uses 1.25 inch then your choices are very wide indeed.

Presumably the scope was purchased used then ?

That top pic looks OK to me. Stop worrying about it and get on and use the scope

The finder arrangements mentioned in other posts, ie: 9x50 RACI optical finder AND a 1x illuminated reticule finder (Rigel Quikfinder in my case) have worked wonders for my deep sky observing over the past few years

Added to the above, I have found having a good hard copy star atlas has been a huge help. In my case I found the Sky & Telescope Pocket Sky Atlas really effective. Using that and the finders mentioned I've had nights with my 12 inch dobsonian when I've found literally dozens of deep sky objects that I've not seen before.

If the scope focuses sharply without the diagonal in place and the diagonal is the only change between that and not being able to get sharp focus, even after adjusting the focus, then the prime suspect becomes the diagonal. It is possible that the mirror of the diagonal is out of position, ie: not at exactly 90 degrees to the light coming down the scope ?

If you bought the scope new, you should really take it up with the vendor and see if they will supply a replacement diagonal.

If the scope was bought used and the diagonal is faulty, you can buy replacements.

I assume that this is your scope ?:

The mirror diagonal with these is pretty basic so it is quite possible that the mirror has come loose.

Have you adjusted the focus to account for the change that the diagonal causes ?. Usually using a diagonal will require you to move the focuser tube inwards 50mm-70mm approx to reach sharp focus again.

I think they are niche instruments but it is a nice niche

These longer refractors do need quite stable mounts though, to give their best performance. The tube length and moment arm force generated have become the challenge for the mount, rather than the tube weight, which is quite modest.

The best tip I can give is to make sure that the finder scope is as well lined up with the main scope view. Finding your targets when you can be confident that your scope is pointing just where the red dot or cross hairs of your finder are pointing is a lot easier !

There is a lovely double cluster below Cassiopeia (the W shape) which is well worth a look at low magnification. It is actually in the constellation of Perseus. Here is a chart:

The clusters are known as NGC 869 and NGC 884 (NGC = New General Catalogue) and should both fit into the same view using the lowest magnification eyepiece.

A nice pair of galaxies under a dark sky are Messier 81 and 82 in Ursa Major. Again use the lowest magnification eyepiece. Here they are:

You can "star hop" to these like this:

My understanding is that the Meade SN's did indeed use spherical primary mirrors but what is harder to find out is the precise focal length of the primary and how it's figure relates to the meniscus lens and the secondary mirror.

Overall I suspect that replacement is going to be both difficult and costly, unfortunately.

11 hours ago, mikeDnight said:

What a fantastic set of observations John. Iras was my first comet. I remember sweeping the sky using 12X60 binoculars until I got cramp in my neck, then as I lowered the bin's, I just glanced upward and there it was, easily visible as a large nebulous fan. 

My early drawings of Jupiter and Saturn weren't nearly as expertly drawn as yours. I used crayola crayons and on occasion felt tips for that road kill effect. When I get chance I'll dig them out and share them. You'll wish I hadn't! 

Thanks Mike - I'd love to see some of your earlier work

It has been interesting comparing my 28 April 1984 sketch with Davids 7 December 2020 drawing here:

https://stargazerslounge.com/topic/367811-mars-7th-december-2020/

When I did my sketch Mars was around 16 arc seconds diameter and for David it was about 14 arc seconds. The scan has lost a bit of the detail and contrast that I captured and the original was pretty close to Davids 2020 drawing.

I must have had sharp eyes back then !

For the scope to work, the focuser tube needs to be moved back away from the secondary mirror to about where I have drawn the red line on the photo below and the focuser tube needs to be able to move smoothly back and forward along the green arrow that I have added in with the eyepiece on the outer end of the tube.

There are probably a number of other adjustments needed but that is the main problem that I see at the moment.

I have never seen a focuser mechanism of that design so it is obviously home made.

Adding another comment is the way to reply. That is the way that the thread on the subject develops.

If you could post some photos of the whole scope as well as the details of how the mirrors are held and the eyepiece is held, then I'm sure you will get suggestions on what to do to make it a workable scope.

With a newtonian scope, the main and secondary mirrors are fixed in position and the focuser / focus tube moves the eyepiece in and out to achieve focus. At no time does the end of the focus tube come anywhere near the secondary mirror.

Here is another design using a single vane to hold the secondary mirror:

The focus tube should be well away from the secondary mirror for the scope to work. The focus tube in the picture seems to be actually pressing against the secondary mirror pushing it out of alignment.

The view down the telescope, towards the main mirror should look something like this with the focuser tube well away from the secondary mirror: