Refractor for visual

[Louis D]

7 hours ago, mikeDnight said:

Hi Geoff,

 I'm talking about an apochromatic refractor such as Michael's lovely Starfield ED above. I've used many ED and Apochromatic refractors and they are in a different league to the SW achromats. I learned that the hard was back in January 2003, when my Helios 150mm F8 achromat was utterly annihilated by a Vixen 102mm fluorite apochromat. The difference was so stark that I never looked through the 150mm achromat again. A couple of years later at an Easter star party at my local astro club, an elderly man who'd looked through every other scope on the field, some very big scopes of every major design, came finally to the Vixen. He took a long look at Saturn, then asked "Why is this one so much better than all the rest"? So even a complete novice with no axe to grind could see the difference.   Back then there were only Vixen, Takahashi, Astrophysics and a new kid TMB. Skywatcher ED's were just about to take the astro community by surprise.

I had the opposite experience 20+ years ago at a local star party.  The Obsession, Starmaster, Star Splitter, Tectron, and Mag-1 Dobs with their premium, hand figured mirrors and hand built mounts were blowing away the Tak and AP refractors on Jupiter, to say nothing of SCTs.  I bought a Dob later that year and have enjoyed it ever since.  I only recently bought a 90mm APO refractor and quite enjoy it as well.  Yes, stars are more pinpoint in the APO, but aperture limits resolution under our steady Texas skies.  It's not unusual to push a 12" to 15" premium Dob to 350x and higher on planets and GCs revealing far more detail than a 4" APO at 200x.

[Beardy30]

Thanks all much appreciated and interesting debate as always 👍🏼

[badhex]

Throwing in my lot with another vote for a 4" doublet, specifically the Starfield 102 as mentioned by @Mr Spock if you're in the UK, or other brandings for elsewhere in the world. 

Obviously it does not have the light gathering of a larger dob but the performance you do get per inch is exceptional. Added to that, with the right EP combo you can easily get 4° of sky at one end and 200x at the other, which is a great spread and covers many objects. 

[Beardy30]

23 minutes ago, badhex said:

Throwing in my lot with another vote for a 4" doublet, specifically the Starfield 102 as mentioned by @Mr Spock if you're in the UK, or other brandings for elsewhere in the world. 

Obviously it does not have the light gathering of a larger dob but the performance you do get per inch is exceptional. Added to that, with the right EP combo you can easily get 4° of sky at one end and 200x at the other, which is a great spread and covers many objects. 

This wee fella ? https://www.firstlightoptics.com/telescopes-in-stock/starfield-102mm-f7-ed-doublet-refractor.html

[badhex]

31 minutes ago, Beardy30 said:

This wee fella ? https://www.firstlightoptics.com/telescopes-in-stock/starfield-102mm-f7-ed-doublet-refractor.html

Yep, that's the badger. Very manageable size and packs a punch, excellent fit and finish to all the components. It's a great scope, can highly recommend.  Obviously you need a mount so that's an additional cost if you don't have one already, but as it is a reasonably small-medium scope you don't need to spend the earth. 

You mentioned AP - not sure if you are intending to explore that at some point but this scope is a touch on the slow side at F7 so you'd probably need a reducer as well as a flattener - but I am not an imager so take with a pinch of salt. 

[Beardy30]

Yea nice beast but too heavy for me at the mo and I’m happy with my visual for now but if I was If I was going AP I’d get a Red Cat 51 - with out any doubt 👍🏼

[mikeDnight]

9 hours ago, Louis D said:

I had the opposite experience 20+ years ago at a local star party.  The Obsession, Starmaster, Star Splitter, Tectron, and Mag-1 Dobs with their premium, hand figured mirrors and hand built mounts were blowing away the Tak and AP refractors on Jupiter, to say nothing of SCTs.  I bought a Dob later that year and have enjoyed it ever since.  I only recently bought a 90mm APO refractor and quite enjoy it as well.  Yes, stars are more pinpoint in the APO, but aperture limits resolution under our steady Texas skies.  It's not unusual to push a 12" to 15" premium Dob to 350x and higher on planets and GCs revealing far more detail than a 4" APO at 200x.

I dream of Texas skies Louis. In 43 years observing from the UK, I've only once seen a Schmidt Cassegrain give a good planetary image. They invariably deliver bland, barely focused planetary images, with stars presenting as blobs rather than stellar points, and soft lunar views. Mak Casse's fare way better for some reason? The 10" F6.3 Dob I had would always resolve more planetary detail than my 4" refractor, but it wasn't as enjoyable to use, and the spider diffraction would spoil the planetary views for me. The 8" was not much better at resolving planetary detail than my 4" which i found surprising, yet it was much more of a beast to handle. Plus, because the 4" is such a good scope, magnifying beyond the 200X resolution limit isn't much of a problem if the seeing is steady; its amazing how much detail is in a small planetary disc when the image scale is increased a little. However, if you know of anyone who would like to buy me a 12" Obsession I woul receiveit gladly. 

[Beardy30]

2 hours ago, mikeDnight said:

I dream of Texas skies Louis. In 43 years observing from the UK, I've only once seen a Schmidt Cassegrain give a good planetary image. They invariably deliver bland, barely focused planetary images, with stars presenting as blobs rather than stellar points, and soft lunar views. Mak Casse's fare way better for some reason? The 10" F6.3 Dob I had would always resolve more planetary detail than my 4" refractor, but it wasn't as enjoyable to use, and the spider diffraction would spoil the planetary views for me. The 8" was not much better at resolving planetary detail than my 4" which i found surprising, yet it was much more of a beast to handle. Plus, because the 4" is such a good scope, magnifying beyond the 200X resolution limit isn't much of a problem if the seeing is steady; its amazing how much detail is in a small planetary disc when the image scale is increased a little. However, if you know of anyone who would like to buy me a 12" Obsession I woul receiveit gladly. 

I agree with your view if the sct - got rid of mine for that very reason 

[Louis D]

2 hours ago, mikeDnight said:

I've only once seen a Schmidt Cassegrain give a good planetary image. They invariably deliver bland, barely focused planetary images, with stars presenting as blobs rather than stellar points, and soft lunar views.

I looked through an 8" Celestron EdgeHD with a 10mm Delos at Jupiter a few years back at a star party, and it was astonishingly sharp.  Apparently, all that extra glass in the corrector puts all the errant SCT light rays where they belong.

2 hours ago, mikeDnight said:

However, if you know of anyone who would like to buy me a 12" Obsession I woul receiveit gladly. 

The 12.5" Mag-1 Portaball I viewed through about 10 or 15 years ago was a lot easier to move around the skies.  The Zambuto primary made Jupiter look like a photograph.  Being on a Osypowski  EQ platform made extended studying of the image a breeze.  Eyepiece balance can be an issue, though.  The owner was using fairly lightweight, but high quality, Plossls.

[SuburbanMak]

There is undoubtedly a "magic' to refractors, pin sharp stars on inky black backgrounds and at shorter focal lengths super-wide views and, well, they look like real telescopes!  There is much wise, experience-based advice above but I would like to put in a word for the humble Mak in the 4-5 inch range, especially if funds are constrained. 

I came back to the hobby 2 years ago after a 35 year break (yikes!) and after much research plumped for a Skywatcher Skymax 127mm, f12 Maksutov as my main telescope, a decision I have not regretted despite picking up several other 'scopes along the way.   There's general agreement that with their long focal length, Maks do well on the Moon and planets - the main reason for discounting them for DSO's being a narrower view (max view a smidge over 1 degree with my trusty SW 127, delivered either by a simple 32mm Plossl at 48x, or 64x with a 24mm, 68 degree EP like my Baader Hyperion). Yes, There are a handful of objects that won't fit into that field - the Pleiades, M31 the Andromeda Galaxy, the Veil nebula and a few more - but I am up to 97/110 Messier objects now with this 'scope and it excels on the less than huge star clusters and brighter planetary nebulae. The narrow view is easily solved with a decent finder scope and RDF combo. 

Double stars are also excellent in the Mak 127, down to its optically theoretical limits (around 1 arc second separation), views are slightly scruffier than a refractor - but it is slight.  

Where I would expect quality to out on a really high quality refractor is the ability to load on very high magnification on those rare nights of exquisite seeing  - I note though that you're in the NW UK, not Arizona.

When it comes to galaxies aperture is surely king, but in the Mak 127 I've seen structure in more objects than I expected to, including some of the fainter Messier galaxies in Virgo/Coma Berenices. This is particularly the case when you get out to a dark site, and this is another area where the Mak shows itself as a really practical observing tool, it is optically excellent (no CA apparent), short, lightweight, very stable in terms of collimation and incredibly robust, rendering it eminently portable and easy to mount (I run mine on an AZGTi GoTo capable mount). People talk about cooling time but at this 5" size in the UK that is rarely an issue (20 minutes or so going out on a freezing cold night last week, often not even noticeable). 

I picked up a basic 10" GSO Dobsonian ahead of spring "galaxy season" last year and it certainly delivers more light on galaxies, resolves more stars in globulars and is stunning on the moon but I find the logistical headache of moving it around & getting it out of my light polluted garden, mean that I reach for it far less often than I do the Mak. 

My point then is that I don't buy that a mid-aperture Mak is pigeon-holed to lunar and planetary views - they deliver great bang for your buck optically. In the end though so much comes down to your own observing routine and preferences & of course, budget. (Full disclosure I hanker after a Tak 4" f9  paired with a widefield Televue 76 as my "desert-island" rig :).  

 

 

[Penumbrella]

10 hours ago, Beardy30 said:

This wee fella ? https://www.firstlightoptics.com/telescopes-in-stock/starfield-102mm-f7-ed-doublet-refractor.html

I see this scope recommended so often - I'm doing a lot of window shopping myself, and, with portability foremost, think I've settled on saving up for a 80mm refractor with a mount like the az-gti (or in that weight class anyway  - maybe the sa gti, the az-gtiX, or the skyhunter). But all of these recommendations for a 100mm refractor makes me wonder if I'd regret getting an 80. Am I right in thinking a 102 refractor would be too much for that kind of mount. And, to avoid derailing this discussion too much, what mount do folks recommend for a 4" refractor? 

[Beardy30]

26 minutes ago, Penumbrella said:

I see this scope recommended so often - I'm doing a lot of window shopping myself, and, with portability foremost, think I've settled on saving up for a 80mm refractor with a mount like the az-gti (or in that weight class anyway  - maybe the sa gti, the az-gtiX, or the skyhunter). But all of these recommendations for a 100mm refractor makes me wonder if I'd regret getting an 80. Am I right in thinking a 102 refractor would be too much for that kind of mount. And, to avoid derailing this discussion too much, what mount do folks recommend for a 4" refractor? 

The mount takes 5kg so I would say it’s too heavy 

[cajen2]

36 minutes ago, Beardy30 said:

The mount takes 5kg so I would say it’s too heavy 

Yes, I've looked into this myself. The 102ED is 4.2 kg, but you have add the weight of a finder, diagonal and EP, so the AZGTi's limit of 5kg would make it very iffy, even if only for visual use. The AZGTIX might be possible. Anyone got another recommendation for a grab&go go-to mount that would take it without spending thousands?

[badhex]

42 minutes ago, cajen2 said:

Yes, I've looked into this myself. The 102ED is 4.2 kg, but you have add the weight of a finder, diagonal and EP, so the AZGTi's limit of 5kg would make it very iffy, even if only for visual use. The AZGTIX might be possible. Anyone got another recommendation for a grab&go go-to mount that would take it without spending thousands?

I have the AZ-GTi and found even an Evostar 80ED a bit much for it, especially with the standard aluminium tripod that it ships with (in some configurations). I suspect it would be a lot better on a better tripod, but it think the 102 is too much even on a good tripod. 

I use the 102 on a scopetech mount zero and Gitzo 5 series tripod. Mainly this is for portability. The scopetech is probably at it's limit with the 102, but having such a sturdy tripod means that it works very well and any vibrations at very high power damp down quickly. Not the cheapest tripod/mount combo though! 

For a much sturdier setup at a much lower cost (but also a lot heavier), the Skytee-2 is very solid and reasonably priced, and could be paired with the standard 1.75" steel Skywatcher tripod, also reasonably priced. I have a skytee which I use with an EQ6 2" tripod and it's insanely sturdy with the 102 on there. 

[bosun21]

56 minutes ago, cajen2 said:

Yes, I've looked into this myself. The 102ED is 4.2 kg, but you have add the weight of a finder, diagonal and EP, so the AZGTi's limit of 5kg would make it very iffy, even if only for visual use. The AZGTIX might be possible. Anyone got another recommendation for a grab&go go-to mount that would take it without spending thousands?

An EQ5 holds the 102 rock steady (about £325) And you can always upgrade it to full go to with a kit

Edited January 24, 2023 by bosun21
Typo

[cajen2]

20 minutes ago, badhex said:

I have the AZ-GTi and found even an Evostar 80ED a bit much for it, especially with the standard aluminium tripod that it ships with (in some configurations). I suspect it would be a lot better on a better tripod, but it think the 102 is too much even on a good tripod. 

I use the 102 on a scopetech mount zero and Gitzo 5 series tripod. Mainly this is for portability. The scopetech is probably at it's limit with the 102, but having such a sturdy tripod means that it works very well and any vibrations at very high power damp down quickly. Not the cheapest tripod/mount combo though! 

For a much sturdier setup at a much lower cost (but also a lot heavier), the Skytee-2 is very solid and reasonably priced, and could be paired with the standard 1.75" steel Skywatcher tripod, also reasonably priced. I have a skytee which I use with an EQ6 2" tripod and it's insanely sturdy with the 102 on there. 

Thanks for that, though I wanted a go-to alt/az mount which is easily portable.

 

16 minutes ago, bosun21 said:

An EQ5 holds the 102 rock steady (about £325) And you can always upgrade it to full go to with a kit

As above, an alt/az mount. The AZ5 wouldn't be man enough.

[bosun21]

Duplicate posting (deleted)

Edited January 24, 2023 by bosun21
Deleted duplicate

[bosun21]

10 hours ago, mikeDnight said:

I've only once seen a Schmidt Cassegrain give a good planetary image. They invariably deliver bland, barely focused planetary images, with stars presenting as blobs rather than stellar points,

You should have collimated it better then. My 8” SCT gives sharp stars and great planetary and lunar images. The images were soft before I learned how to collimate it correctly.

[bosun21]

18 minutes ago, cajen2 said:

As above, an alt/az mount. The AZ5 wouldn't be man enough.

So you only want an alt/az mount that can be upgraded or come with go to? The skytee has not got any upgrade to go to that I know of. You are looking at a slice of money for a decent alt/az go to. (Rowan)

Edited January 24, 2023 by bosun21
Typo

[Beardy30]

Why not keep the mount and change the OTA - the80Ed would be too heavy but you could look at the sharp star 61EDPH on the AZI GTI and it would do well on the eq wedge for AP and imaging

[badhex]

45 minutes ago, cajen2 said:

Thanks for that, though I wanted a go-to alt/az mount which is easily portable.

Bit of a "cheap/fast/good, pick two" situation unfortunately I think. Goto, alt-az and portable generally will come at a significant cost, e.g. Rowan or one of the newer harmonic drive alt-az mounts. 

Although it's not a goto, this is also somewhat true of the manual setup I mentioned earlier with the Gitzo and Mount Zero. I was using the Skytee and EQ-6 tripod, but it was a total pain lugging everything up and down two flights of stairs, so I spent ages trying to find something that would be as light as possible but still take the 102 happily. I eventually settled on the Gitzo/Zero which ticks those boxes but between the two items it cost me ~1500 eur for the privilege. Worth it, though 🙃

Edited January 24, 2023 by badhex

[mikeDnight]

34 minutes ago, bosun21 said:

You should have collimated it better then. My 8” SCT gives sharp stars and great planetary and lunar images. The images were soft before I learned how to collimate it correctly.

That would presume that every SCT I've used, none of them mine, were out of collimation, which is definitely not the case.  I've been in the game long enough to recognise an out of collimation image. When compared to every other design of scope, SCT's have proved themselves time and again to be the over all worst visual instrument I've ever encountered. As I mentioned in a previous post, I've only seen one SCT, an old 1980 orange C8, in 43 years that gave a stunning view of Jupiter. As a visual lunar and planetary observer, a classical Cassegrain or Mak Cass would be a preferred choice for me. I am happy you have a good SCT though!

[Mr Spock]

56 minutes ago, bosun21 said:

You should have collimated it better then. My 8” SCT gives sharp stars and great planetary and lunar images. The images were soft before I learned how to collimate it correctly.

I found the same. My former C9.25 gave really crisp images when collimated properly - on the right night; it was susceptible to poor seeing conditions, more than other types of scopes. I did very easily split a 0.7" double with it. Something no small refractor could ever do 
Oh, and Damien Peach seemed to like his too...

[mikeDnight]

Schmidt originally designed his telescope to be a camera, so it's not surprising that's where it shines. DP is an imager not a visual observer, and so it's not surprising his choice of telescope is a Schmidt Cassegrain.

[bosun21]

6 hours ago, mikeDnight said:

That would presume that every SCT I've used, none of them mine, were out of collimation, which is definitely not the case.  I've been in the game long enough to recognise an out of collimation image. When compared to every other design of scope, SCT's have proved themselves time and again to be the over all worst visual instrument I've ever encountered. As I mentioned in a previous post, I've only seen one SCT, an old 1980 orange C8, in 43 years that gave a stunning view of Jupiter. As a visual lunar and planetary observer, a classical Cassegrain or Mak Cass would be a preferred choice for me. I am happy you have a good SCT though!

I get it that you are an out and out refractor man, and more power to you for it. However all I am saying is that after I learned to collimate it accurately the images were very pleasing. I will admit that they don’t punch through bad seeing in the way that a nice apochromatic refractor does, and the refractor has better contrast. However as most of the year as  I will be doubles and galaxy observing the SCT and the 12” dobsonian are my tools of choice. May the planets be kind to you. Clear skies 🔭