Stellamira 110ED or SW 150PDS?

[WolfieGlos]

I currently image with a 72ED refractor, but looking for a bit more reach for galaxy season so looking for my second scope.

I have a HEQ5 + belt mod, 2x DSLR's (modded and unmodded) and run my whole setup through Stellarium, ASCOM, NINA and phd2.

So I'm a bit torn between going with a refractor or a reflector. I'm currently thinking either a Stellamira 110ED https://www.firstlightoptics.com/stellamira-telescopes/stellamira-110mm-ed-f6-refractor-telescope.html or a Skywatcher 150PDS https://www.firstlightoptics.com/reflectors/skywatcher-explorer-150p-ds-ota.html . 

I quite like the thought of the 110ED as it's more compact for storage with the same f/ ratio I currently have with my 72ED, but the reflector has a bit more reach and is a bit faster. Diffraction spikes won't bother me.

Does anyone have experience with the above scopes? Or does anyone have any other recommendations?

I also run guiding with the ZWO 30mm scope + ASI 120MM; is this suitable for these longer focal lengths?

[bosun21]

Personally I would go for the Starfield 102. For an extra £100 you get better optics with FPL53 and Lanthanum glass over the FPL51 in the Stella Mira. It’s f7 but with the 0.8x reducer/flattener it comes out at f5.6.

[Rallemikken]

44 minutes ago, WolfieGlos said:

Or does anyone have any other recommendations?

The Sky-Watcher Explorer 150PDS (750mm) will be short for galaxies. I have a 200 PDS (1000mm) and I would like to have an additional 200-500mm. If you have decided on 6" I'd go for the Sky-Watcher Explorer 150PL with 1200mm focal lenght. Especially if you image with DSLR, as I do. Only a handful of galaxies are bigger than 25 arcminutes, most are smaller than 15. The 150PDS and a Canon 600D is 102 minutes wide. M82, the Cigar Galaxy, is 11 minutes wide. And that's midsize.

[Elp]

If you want reach in a small form factor consider a SCT. It's not the first thing which comes to mind for imaging, but it fit my requirements and the 130pds was sold on. Yes a refractor and Newtonian are sharper, but I was pleasantly surprised how much more detail (resolution) was achieved with my 150mm SCT compared to my 60mm refractor.

[WolfieGlos]

12 hours ago, bosun21 said:

Personally I would go for the Starfield 102. For an extra £100 you get better optics with FPL53 and Lanthanum glass over the FPL51 in the Stella Mira. It’s f7 but with the 0.8x reducer/flattener it comes out at f5.6.

Thanks, that’s a nice looking scope but with the price and flattener it’s a bit more than I wanted to spend…. something I crucially didn’t mention in the original post. I already have a stellamira flattener so the cost would be just the scope if I went with the 110ed. Willing to save a bit longer if it’s the right one though.

11 hours ago, Rallemikken said:

The Sky-Watcher Explorer 150PDS (750mm) will be short for galaxies. I have a 200 PDS (1000mm) and I would like to have an additional 200-500mm. If you have decided on 6" I'd go for the Sky-Watcher Explorer 150PL with 1200mm focal lenght. Especially if you image with DSLR, as I do. Only a handful of galaxies are bigger than 25 arcminutes, most are smaller than 15. The 150PDS and a Canon 600D is 102 minutes wide. M82, the Cigar Galaxy, is 11 minutes wide. And that's midsize.

Interesting, I viewed several targets in Stellarium with the 150pds and it seemed OK to me! I did consider the 200pds but have read it’s a bit on the limit for the HEQ5. 
The 150PL… wow, that’s a scope! I’m considering it, especially for the price and focal length but possibly a bit large if I leave it setup in the living room like I do currently! Discussion with the wife to follow….

11 hours ago, Elp said:

If you want reach in a small form factor consider a SCT. It's not the first thing which comes to mind for imaging, but it fit my requirements and the 130pds was sold on. Yes a refractor and Newtonian are sharper, but I was pleasantly surprised how much more detail (resolution) was achieved with my 150mm SCT compared to my 60mm refractor.

I’m not familiar with SCT’s at all, but on some quick google searches they appear to be expensive in the Celestron range. Is there much difference to a RC or classical cassegrain? They both are a lot slower at f9 or f12 but seem to be used for the same purpose according to the blurb. Examples below: 
https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-6-f9-m-crf-ritchey-chrtien-telescope-ota.html

https://www.firstlightoptics.com/stellalyra-telescopes/stellalyra-6-f12-m-crf-classical-cassegrain-telescope-ota.html

[Elp]

16 minutes ago, WolfieGlos said:

I’m not familiar with SCT’s at all

I believe the main difference between an RC and SCT is the RC doesn't have a front glass corrector plate. The RC has slightly different mirror designs to account of optical correction and their apertures are not limited.

The reason I chose my C6 was it's FL to size ratio. It's quite small but packs 150mm aperture and native 1500mm focal length at F10. I can use the F6.3 reducer to get it down to 1045mm FL, and a Hyperstar for 307mm FL imaging only at F2. I can use it for visual and imaging. No other scope out there gives you this level of flexibility and adaptability as far as I'm aware. The larger aperture Celestrons will provide you greater FL as you go up the range.

You can buy the Celestron SCTs as OTA only. If you're patient many come up used and mine didn't cost much at all.

The one thing I would say focus or contrast can seem a little "soft" compared to a refractor or a Newtonian, but it doesn't bother me considering everything else especially having to store it indoors after use, I can pack it away into a backpack which also allows me to take it places easily too.

[Rallemikken]

2 hours ago, WolfieGlos said:

I viewed several targets in Stellarium with the 150pds and it seemed OK to me!

Don't use the images in Stellarium for framing, they are not always sized correct.

http://astronomy.tools/calculators/field_of_view/?fov[]=40||37||1|1|0&fov[]=53||37||1|1|0&messier=82

Pure maths. This camera is 5184 pixels wide. With the shortest scope M82 will cover only 570 pixels in width. That is not much room for details. One may argue that the shorter scope is faster, but in this case it will be fast in only gathering black emtyness. If you plan to spend some time on this, you will very fast run out of reasonably big galaxies. They are small. And don't even consider a barlow. Been there, done that. The whole point of the reflectrors is to avoid any glass between the target and the sensor. The long 6" will give good perfomance without any correctors, anyway, with galaxies we always put them in center, don't we??

[WolfieGlos]

2 hours ago, Elp said:

I believe the main difference between an RC and SCT is the RC doesn't have a front glass corrector plate. The RC has slightly different mirror designs to account of optical correction and their apertures are not limited.

The reason I chose my C6 was it's FL to size ratio. It's quite small but packs 150mm aperture and native 1500mm focal length at F10. I can use the F6.3 reducer to get it down to 1045mm FL, and a Hyperstar for 307mm FL imaging only at F2. I can use it for visual and imaging. No other scope out there gives you this level of flexibility and adaptability as far as I'm aware. The larger aperture Celestrons will provide you greater FL as you go up the range.

You can buy the Celestron SCTs as OTA only. If you're patient many come up used and mine didn't cost much at all.

The one thing I would say focus or contrast can seem a little "soft" compared to a refractor or a Newtonian, but it doesn't bother me considering everything else especially having to store it indoors after use, I can pack it away into a backpack which also allows me to take it places easily too.

Thanks Elp. To be fair, the price I looked at included mount for the C6 but good call on second hand OTA only. I’ve previously not looked at these scopes at all, but that hyperstar is incredible for what it’s able to do at f2 with that scope, and the options with a reducer like you say, that’s great flexibility. 

If you don’t mind me asking, what are they like to collimate? 

[Elp]

To be honest, I've never seen a reason to collimate mine, airy disk looks fine, stars look fine, planets look fine. Even whilst imaging. And I always setup fresh and pack away again so it's not like the scope isn't being moved. The HS is different, but again, my lens was quite well corrected at zero gap position so I've never felt the need to adjust it, if I'm picky I probably would but I normally crop images anyway if edge stars are an issue, centre seems okay.

If you had to collimate at native FL, it's just the three secondary mirror adjustment screws up front which is quite easy. The HS uses three screws also and replaces the secondary mirror.

People say they suffer from mirror flop when doing a positional change or meridian flip, but I haven't really noticed much of a change.

Edited April 2, 2023 by Elp

[Clarkey]

On 01/04/2023 at 22:29, Rallemikken said:

The Sky-Watcher Explorer 150PDS (750mm) will be short for galaxies. I have a 200 PDS (1000mm) and I would like to have an additional 200-500mm

You do need to consider the quality of the seeing. I have a 115mm refractor and an RC8 with about 2x the focal length. In reality the quality of the image is similar with both, with the RC8 binned x2 to give around 1"/pixel. The RC8 just ends up faster due to the larger aperture at the same pixel scale.

The two images below are examples. The first is the RC8, the second the 115mm triplet. Ignoring the colours and processing, the detail is similar on both.

[Rallemikken]

1 hour ago, Clarkey said:

You do need to consider the quality of the seeing. I have a 115mm refractor and an RC8 with about 2x the focal length. In reality the quality of the image is similar with both, with the RC8 binned x2 to give around 1"/pixel.

I'm slowly accepting that focal lenght ain't king, done some testing myself lately. The one that started this topic had a HEQ5. Maybe an 8" f/5 or the shorter 8" f/4 (if wind is an issue) would be the better choice. Most bang for the bucks. Don't think a triplet was on the table. Costly. And I wouldn't go under 800mm for a dedicated galaxy rig, regardless. 800-1000mm would suit the slightly older Canon cameras like the 450D, 600D and 5D MkII. I see that 1200mm might be a little long for those.

[WolfieGlos]

Still not made up my mind which way to go on this one, but luckily my Canon's are a bit newer (800D and 77D).

I was learning towards a 6" RCT which gives good FL on M63, but having watched a few videos on collimation made me think twice. Considering other accessories, i.e. flatteners/reducers/coma-correctors, flat panels, collimation devices, etc, it all starts to add up. No issues with this, just want to go in with my eyes a bit more open than when I got my first scope, the 72ED.

I am also considering the SW Startravel 150, 750FL at f/5 with a direct DSLR connection, i.e. no flattener, seems like a good choice to my mind? No other costs. It's not a scope I see many people use and post images with, and I'm wondering why....

[Clarkey]

11 hours ago, Rallemikken said:

I'm slowly accepting that focal lenght ain't king, done some testing myself lately. The one that started this topic had a HEQ5. Maybe an 8" f/5 or the shorter 8" f/4 (if wind is an issue) would be the better choice. Most bang for the bucks. Don't think a triplet was on the table. Costly. And I wouldn't go under 800mm for a dedicated galaxy rig, regardless. 800-1000mm would suit the slightly older Canon cameras like the 450D, 600D and 5D MkII. I see that 1200mm might be a little long for those.

All completely valid points. I was just trying to highlight to the OP that FL was not necessarily critical and in most cases, over about 800mm you will not gain resolution (but you might get improved speed).

[Clarkey]

11 hours ago, WolfieGlos said:

and I'm wondering why....

You will get awful chromatic aberration with the ST150. Go for an ED doublet as a minimum for imaging if you are looking at the refractor route.

The RC6 is a good scope, but you will need a flattener and I'm not sure how large the imaging circle is for larger sensors. The RC8 is usable without a flattener, but is at the limit for an HEQ5, even with an OAG. Collimation is tricky - but with care is not too bad.

I have recently purchased a 115mm triplet (Altair Starwave) and am using it with the standard StellaMira field flattener and small guidescope. I have not used it much as the weather has not been kind this winter. However, the images I have managed have been very good. Maybe more than you want to spend - but a possible option. If you are budget limited, the newtonians are a good choice in terms of value for money. Personally, I would go for an F5 as the upgrades required for the cheaper F4's are not worth the cost.