John

9 minutes ago, nightfisher said:

I would post a pic of my one and only frac, but it has not been out since buying it about 4 months ago, the Opticstar AR90

You could still post a pic - it might inspire you to look though it if the sky is clear !

Great to see the big Vixen again - used to be my dream scope following the Astronomy Now review way, way back

Good to see the ED102 F/9 riding nicely on an AZ-4 as well. I'm still pondering on an AZ-4 as a lighter option to the Skytee II for the Tak FC-100DL 

Nice Japanese glass

The Vixen rep at the astro show last month confirmed to me that the LVW's are definitely out of production now so pick them up while you can !

I asked if they had a successor planned and he pointed to the SSW's but I had to point out that they did not really fill the same niche. 

Hello and welcome to the forum.

I can't help you on these issues but I've found a website which might be worth reading. It includes some of the maths involved in black holes:

http://physicsforidiots.com/space/black-holes/

I've been doing a lot of reading on HA solar scopes recently and one thing that has really struck me is the variation in performance reported between individual units, of all brands and designs. I wonder, if you lined up half a dozen examples of the same scope model and viewed through each one under the same conditions, same magnification etc, etc, whether any of them would be exactly the same ?.

Edit: It also occurs that maybe, if you repeated the excercise on another occasion the results would differ again ?

This is very timely for me Mark. Thanks for posting this report

Seben don't generally get good reviews but it might be OK for that price. I use 6x30 RACI's (Skywatcher) on my smaller aperture refractors and they do a decent job but for a larger aperture scope I think the 50mm aperture is strongly preferrable, if you can get one. I prefer RACI which shows the sky as my eye sees it and as my star maps show it. I can cope with the inversion / reversal when I look through the eyepiece of the scope !

The trouble with realy cheap finders is that they can have poor, non-achromatic objectives and also can be stopped down to an even smaller aperture !. So it could be a false economy, if you see what I mean.

A half decent 9x50 raci is going to cost around £40 on the used market.

Faced with having to do something to improve the useability of the scope for £15 I'd probably go for a low cost red dot finder in place of the 8x50 straight through, get it really well aligned with the main scope, and manage with that until I had the funds for what I find is the ideal setup on a medium to large dob which is a 9x50 RACI partnered with a Telrad or Rigel Quickfinder.

31 minutes ago, 25585 said:

I hope one night to see an elliptical galaxy. They have always fascinated me as older DSOs further back in time still - nearer the beginning of our Universe. 

And that is one of the wonders of naked eye observing to me, looking at an image that has reached us projected by an object which may no longer exist or be as we see it today. 

There are a few Quasars visible in 12" scopes which might be of interest:

Here is the definition:

Field Curvature

If star images near the field’s center are in focus when those near the edge are not, and vice versa, then the eyepiece suffers from field curvature. This is a familiar effect for owners of Schmidt–Cassegrain telescopes, because the focal plane of such telescopes is not flat but strongly curved.

I guess this also shows why field curvature in eyepieces can actually improve the performance of the scope, as long as it is the opposite type to that which the scope itself delivers. If the eyepiece is delivering FC that adds to that which the scope delivers than things are not likely to be as satisfactory.

The complete scope and mount is shown in the photo in the 1st post in this thread. Thats how you use the scope but obviously it would be pointing more "skywards" so the eyepiece would be at a more reasonable height for a seated observer. Something like this (this is the 10 inch non motorised version):

If you want to get really close to the eye lens you can unscrew the top section of a Pentax XW eyecup leaving the eyelens very close to the top of the eyepiece:

2 hours ago, 25585 said:

Surprised FLO do not sell those (or Tele Vue).

FLO do sell the Maxvision's but the Meade 5000 series SWA's and UWA's are now out of production I believe. The story goes (as I understand it) that the Meade decided to change direction but the manufacturer had made quite a few of the SWA's and UWA's which Meade did not take up so they re-branded them Maxvision and distributed them at a somewhat discounted price.

I expect FLO would like to carry Tele Vue's and are working on it

1 hour ago, 25585 said:

Shifted to a 40mm LV wish, a fl I don't own, than can be Barlowed to a 20, albeit with narrow field. 

John (as you know) eye relief is my #1 consideration. How much er is lost on current LVs when the eye cups are screwed fully down, compared to the up-or-down folding cups of original LVs? My 10 and 6 allow whole fov with glasses and less exact eye placement to achieve that.

32mm is covered by the excellent TV Plossl, a LV 40mm 31.7mm would complete my travelling set and fit in an ep bandolier.

 

 

I can't really answer that I'm afraid. I felt that the eye relief of the SLV's was more than comfortable and very similar to the Pentax XW's or TV Delos and that was more than enough for me so I concentrated my review on their other properties.

I guess a current SLV owner might be able to answer your question and possibly post a photo of the top of an SLV with the eye cup in it's lowest position ?

As eye relief is so critical for you, I feel that you might want to focus on eyepieces with apparent fields of view of 60 degrees or less as with the narrower fields, seeing the whole thing is easier.

Also eyepieces with less wide fields are likely to have eye lenses that are less concave so the quoted eye relief is more likely to be useable to a greater extent.

There are some designs, eg: the Maxvision and Meade 5000 series SWA's and UWA's where the top section of the eyepiece can be removed completely which leaves the eye lens right at the top of the remaining eyepiece body. Like this:

1 hour ago, DRT said:

.... I've also switched from Ethos to Delos eyepieces so that will lighten the load considerably ?

The longer FL's are certainly lighter but the 8 and 6 Delos actually weigh a touch more than the equivilent Ethos, rather to my surprise.

I have the 17.3 Delos and it's a very nice eyepiece

That looks very impressive Derek

It's going to be quite a stack with a big 2" eyepiece in the focuser. No chance of tube flex with the weight out that far is there ?

2 hours ago, 25585 said:

... trapped in the dream v reality spiral!

Sometimes also known as "paralysis by analysis"

On 03/09/2017 at 20:20, 25585 said:

Thinking about the 20mm, but have an Erfle of same fl. Would the SLV be signifigantly better?

Sorry for the late reply - I've been away on holiday.

The SLV would be sharper across the whole field of view than the Erfle even in faster scopes and the light transmission and light scatter control is likely to be improved by the latest glass and coating types used in the SLV design.

I realise that you have probably made another choice now but I thought I'd respond to this question all the same

I do remember Dark Star - I have a brochure of theirs somewhere I'm sure

About the only affordable big aperture scopes a couple of decades back.

Climbing a number steps with a scope puts a whole different spin on the weight and portability of a scope. I have a short, flat carry to my observing place so moving my 12" do there in two short carries is no problem - it takes just a minute to set the thing up. If I had to climb up and down some stairs it would not be practical at all for me.

Each of our circumstances is a little different and it's taken some time to realise what works for me. My previous 12" dob was a Meade Lightbridge which was much heavier than my current Orion Optics 12" dob. Ergo, the Meade did not get used much

On cooling fans, I don't find that I need one (even though I have one fitted) with my 12" dobsonian.

My 12" weighs the same as most 10" dobs so it gets used lots !

Can't recall if I've posted these

My TMB / LZOS 130mm F/9.2 triplet refractor on the HEQ5 mount / Berlebach Uni 28 tripod. I used this setup last night and may well do the same tonight

9 hours ago, Frank the Troll said:

I brought the mirror set off astro buy sell, at the time it was listed as F4.7 but could easily be different

The pic is the old cell it was in, quite a big heavy lump of metal, now replaced with a wooded 9 point

That looks just like the older type Synta 10" mirror cell 

49 minutes ago, Frank the Troll said:

Here's a little home made dod. All the bits and pieces are 2nd hand

Tube sourced from Orion as old stock no longer needed

10.5" F4.7 mirror.  The base I brought for peanuts is from a 12" so needed to trim it down a bit

Mirror cell upgraded to 9 points, SW focuser, that will be upgraded at some point

Nice looking scope - looks more like the F/6.3 version though

I believe that Giro mounts have dual 3/8ths / M10 compatible threads in their bases which is helpful.

Nice report

I had a play with an AZ5 at an astro show recently. The mount head seemed nice but the tripod......

Seems a shame to have to lash out £60 to use the head on a standard EQ5 / HEQ5 / CG5 tripod to gain stability. There must be a lower cost way to adapt it / the tripod hub

Presumably, if the "north peg" was not on the top of the tripod hub, the only remaining obstacle is that the AZ5 uses a 3/8ths inch thread rather than the M10 that the EQ5 / HEQ5 etc use ?