More Portable Scope - Sensible Choice?

[Roog]

23 hours ago, Zeta Reticulan said:

Patrick Moore once stated that a 4" refractor was roughly equivalent to a 6" reflector.

Interesting, I have not heard this one before, is this generally accepted and if so why does this come about? Do lenses transmit more light than mirrors for a given aperture or is there another characteristic in action here ? 

[RobertI]

37 minutes ago, Roog said:

Interesting, I have not heard this one before, is this generally accepted and if so why does this come about? Do lenses transmit more light than mirrors for a given aperture or is there another characteristic in action here ? 

I’m sure this question will generate a lot of answers! My understanding is that unobstructed aperture of the refractor allows for greater contrast and cleaner images which can make up for its lack of aperture and potentially provide better views certain objects such as planets. I would have thought greater resolution of a 6” Newtonian will always give better views of objects such as globular clusters and should reveal fainter DSOs. So as a very general statement it is probably true but depends a lot on what you enjoy looking at. 

Edited September 2, 2022 by RobertI

[Elp]

I would never sell my WOZ61, it is that good at everything I've used it for, visual and imaging. No doubt a larger aperture will show more (as I experienced with a guide scope bump up from 30mm to 50mm), but can't beat the size and weight of the Z61, I also have a choice of flattener to use with it for adjustable FL, FStop and FOV.

[SthBohemia]

1 hour ago, Roog said:

is there another characteristic in action here ? 

^^ Yes.. Quality of the optics. A 4" refractor from Takahashi, Istar, TeleVue, Astro Physics etc will make mince pies out of any of the 6" Chinese made reflectors. 

Maybe a comparison between a high end reflector such as a Cave (with modern coatings) and the above fracs might provide some answers.

Got to remember P.Moore wrote most articles many years ago before the advent of the enhanced mirror coatings, a NEW aluminium coated mirror was approx 84% reflective and a silvered one 92% (for a few days). Which equates to a damn lot of 'lost' light through 2 mirrors, add secondary obstruction, vane diffraction etc etc etc...

edit- Quality of the optics AND the quality of the construction. The most obvious difference between a Meade EXT, a C90 and a 3.5" Questar seems to be the quality of construction along with PROPER collimation.. see below.. 

https://www.scopereviews.com/90mmComparo.html

Edited September 2, 2022 by SthBohemia

[Zeta Reticulan]

2 minutes ago, SthBohemia said:

^^ Yes.. Quality of the optics. A 4" refractor from Takahashi, Istar, TeleVue, Astro Physics etc will make mince pies out of any of the 6" Chinese made reflectors. 

Maybe a comparison between a high end reflector such as a Cave (with modern coatings) and the above fracs might provide some answers.

Got to remember P.Moore wrote most articles many years ago before the advent of the enhanced mirror coatings, a NEW aluminium coated mirror was approx 84% reflective and a silvered one 92% (for a few days). Which equates to a damn lot of 'lost' light through 2 mirrors, add secondary obstruction, vane diffraction etc etc etc...

My Chinese 4" ED refractor has Japanese FPL-53 glass. Although much of that glass is actually made in China now.

[Zeta Reticulan]

1 hour ago, Roog said:

Interesting, I have not heard this one before, is this generally accepted and if so why does this come about? Do lenses transmit more light than mirrors for a given aperture or is there another characteristic in action here ? 

The larger reflector will have greater resolution. My guess is that refraction is more efficient and there is no obstruction. So better contrast and acuity. 

[Stu1smartcookie]

Hi Roog , 

So a few choices for you from the comments . If i can  maybe add... I currently have a lovely 60mm Horizon refractor which is fantastic for widefield visual and of course ( although i have yet to use it with a camera ) its great for photography , its a good compliment to your Dob , but , having owned an 80ed i would have to say i second Stu's suggestion that the 80 mm is a good choice as it gives extra apperture for visual and can still be a great tool for photography. Also the 150mm heritage dob gets a great write up . But , pinpoint stars in a refractor are a joy to behold . 

Edited September 2, 2022 by Stu1smartcookie

[Louis D]

Here's an Ed Ting comparison between a reflector, a refractor, and a Maskutov to see which yielded the best images.

[SthBohemia]

On 31/08/2022 at 23:29, Roog said:

but I have a vision of a 80mm ED refractor

Just to add to the 'pile' of suggestions...

Go 4 quality rather than the mass produced scopes with very low quality control, maybe a 60-80mm Takahashi or similar high end scope, second hand if possible...

How about this thing- https://www.astrobuysell.com/uk/propview.php?view=190282 it's even a wonderful ORANGE tubed SCT complete with a Torrence.Ca label 🙂 

Edited September 2, 2022 by SthBohemia

[RobertI]

25 minutes ago, Louis D said:

Here's an Ed Ting comparison between a reflector, a refractor, and a Maskutov to see which yielded the best images.

Nice comparison, although admittedly on premium scopes. So basically (spoiler alert) the 5” apo refractor and the 7” premium Newtonian gave similar performance overall, beating the Intes 6” compound scope. Kind of backs up the traditional wisdom about 4” fracs and 6” Newts being similar performance. But the article also makes the point that you can enjoy whatever scope you happen to possess!

Edited September 2, 2022 by RobertI

[Louis D]

1 minute ago, RobertI said:

Nice comparison, although admittedly on premium scopes. So basically (spoiler alert) the 5” apo refractor and the 7” premium Newtonian gave similar performance overall, beating the Intes 6” compound scope. Kind of backs up the traditional wisdom about 4” fracs and 6” Newts being similar performance. But it also makes the point that you can enjoy whatever scope you happen to possess! 

At least it was a fair fight.  It wouldn't have made sense to compare scopes of different refinement levels.

[cajen2]

1 hour ago, Louis D said:

At least it was a fair fight.  It wouldn't have made sense to compare scopes of different refinement levels.

Not exactly fair when you factor in the price! 

Also note that this test was 15 years ago. I wonder what scopes people would choose for a similar test now....

[SthBohemia]

1 hour ago, RobertI said:

Here's an Ed Ting comparison between a reflector, a refractor, and a Maskutov to see which yielded the best images.

Only problemo which you plainly state @RobertI is they are all high end scopes. Be interesting if he happened to throw a Chinese made scope or 2 into the fray! However, that might be akin t throwing a sparrow amongst the vultures 😞 

The Oak scopes have always left me dumbfounded, having made many mirrors it astounds me that they are figured 1/74th!! If I get one to 1/16th I consider I have done extremely well.. 

[Louis D]

10 minutes ago, cajen2 said:

Also note that this test was 15 years ago. I wonder what scopes people would choose for a similar test now....

Until recently, Teeter was still making solid tube Dobs with Zambuto mirrors.  TEC makes pretty decent APOs.  I'm not sure about a modern, high end Mak-Newt.

[Louis D]

5 minutes ago, SthBohemia said:

Only problemo which you plainly state @RobertI is they are all high end scopes. Be interesting if he happened to throw a Chinese made scope or 2 into the fray! However, that might be akin t throwing a sparrow amongst the vultures 😞 

The Oak scopes have always left me dumbfounded, having made many mirrors it astounds me that they are figured 1/74th!! If I get one to 1/16th I consider I have done extremely well.. 

Chinese scopes in 2007 were pretty bad in comparison.  Mechanically, optically, etc. they were just no where close to the same league.  It would be interesting to test again to see if there is much of a visual difference between a Chinese APO and a TEC/AP APO or between a Zambuto mirror equipped Dob and a Chinese made Dob.  I know Teeter had a GSO mirror option, so they couldn't have been all that bad.

Edited September 2, 2022 by Louis D

[Mr Spock]

There is a difference in quality between inexpensive scopes and expensive scopes - you get what you pay for. Country of manufacture is irrelevant though some people seem obsessed by it. Without these inexpensive mass produced scopes many people wouldn't have the opportunity to do astronomy at all.

[SthBohemia]

6 minutes ago, Mr Spock said:

Without these inexpensive mass produced scopes many people wouldn't have the opportunity to do astronomy at all.

60 years ago, age 15, I made a 6" newt AND the equatorial mount from scrap metal acquired from junkyards. Could not afford an aluminising service thus silvered the mirror...

If one is interested enough ONE finds a WAY 🙂 ....

[Stu1smartcookie]

34 minutes ago, Mr Spock said:

Without these inexpensive mass produced scopes many people wouldn't have the opportunity to do astronomy at all.

Absolutely , i know it doesn't seem so to many but telescopes are relatively cheap now compared to years ago . And those mass produced scopes are good products . 

[Stu]

Interesting discussion notwithstanding, let’s try to keep this relevant to answering the OP’s question. Thanks 👍

[Mr Spock]

My suggestion would be the Heritage 150P https://www.firstlightoptics.com/dobsonians/sky-watcher-heritage-150p-flextube-dobsonian-telescope.html

Small, portable but not small in performance. It's fitted with a standard Vixen dovetail so you can dismount it and attach to a larger mount if you wish. 

I quite fancy one myself!

[cajen2]

1 hour ago, Mr Spock said:

My suggestion would be the Heritage 150P https://www.firstlightoptics.com/dobsonians/sky-watcher-heritage-150p-flextube-dobsonian-telescope.html

Small, portable but not small in performance. It's fitted with a standard Vixen dovetail so you can dismount it and attach to a larger mount if you wish. 

I quite fancy one myself!

Indeed. Mine makes a great grab & go scope: I can pick up the whole thing (including mount) in one hand, it's so easy to store and the optics are much better than you.might suppose. I had debated getting a (say) 80 mil frac on a lightweight mount but I honestly can't think of any advantage to that. Once you've sorted the focuser, it's a cracker.

[Astro_Dad]

Another thread almost full circle again! You won’t be surprised to hear I fully endorse the Heritage 150p option - see earlier 👍

Edited September 2, 2022 by Astro_Dad

[Roog]

Its all good if a little bewildering, thank you everyone. 

It would be really nice to get a high quality 4" refractor, but I notice the price rises very quickly once you get North of 80mm including the increased size and weight for a portable camping scope.

I will keep an eye on the used ads and torture my self trying to choose!

 

Thank you  

[Stu]

18 minutes ago, Roog said:

Its all good if a little bewildering, thank you everyone. 

It would be really nice to get a high quality 4" refractor, but I notice the price rises very quickly once you get North of 80mm including the increased size and weight for a portable camping scope.

I will keep an eye on the used ads and torture my self trying to choose!

 

Thank you  

It’s tricky isn’t it!

There used to be a 102mm f7 from Altair Astro for around £500 which uses FPL-51 glass I think but I know @ScouseSpaceCadet is pleased with his. Can’t see it listed currently.

You are right about size and weight increasing too, although you would probably end up with a similar mount for either 80 or 100mm eg something like an AZ4 or 5. Might not end up being a huge space saving though.

The Evolux 82mm from a Skywatcher looks nice, and worth considering. Has a sliding deshield so is a bit more compact.

https://www.firstlightoptics.com/pro-series/sky-watcher-evolux-82ed-ota.html

[ScouseSpaceCadet]

8 minutes ago, Stu said:

It’s tricky isn’t it!

There used to be a 102mm f7 from Altair Astro for around £500 which uses FPL-51 glass I think but I know @ScouseSpaceCadet is pleased with his. Can’t see it listed currently.

You are right about size and weight increasing too, although you would probably end up with a similar mount for either 80 or 100mm eg something like an AZ4 or 5. Might not end up being a huge space saving though.

The Evolux 82mm from a Skywatcher looks nice, and worth considering. Has a sliding deshield so is a bit more compact.

https://www.firstlightoptics.com/pro-series/sky-watcher-evolux-82ed-ota.html

https://www.altairastro.com/starwave-ascent-102ed-f7-refractor-telescope-geared-focuser-468-p.asp

Unfortunately, very recently the price of the 102 f7 and 80mm f7 have increased by £100. ☹️

At £495 I felt the 102ED was a huge bargain. It's set up now waiting for this evening's Io shadow transit.

The 102ED f11 has dropped in price a touch though and reviews have been good.

Edited September 2, 2022 by ScouseSpaceCadet
F11