Lee_P

42 minutes ago, catburglar said:

But that’s with a 70mm refractor, not a sail disguised as an 8inch Newtonian…I think the 6inch mak newt should be nice quality and no issues with spacing/back focus. 

Yes ok, that's a good point. The Explore Scientific MN152 does seem like it could be a good option. And no backfocus issues you say..?

17 minutes ago, catburglar said:

The OP states that his specific aim was to get “closer in” to his targets…So this means imaging at a more higher image scale. Currently he’s at approx1.9 arcsec per pixel and with good guiding on a HEQ5he may be able to get to somewhere around 1.2 arcsec per pixel (this will require a guiding accuracy of around 0.6 arcsec RMS). 1.2arcsec per pixel requires a focal length of around 650mm with the 2600camera- so the 107PHQ is a bit longer than you need, but if you regularly get guiding errors lower than 0.6 RMS then you may be able to make use of the extra FL. I’d expect an 8inch newt on the HEQ5 might be pushing it a bit on all but the very best (and calmest) of nights. A 6inch F5 with coma corrector may be the sweet spot.

Thanks for the input! My mount is on a pier and I do often have an RMS around 0.6. 

1 hour ago, Rallemikken said:

First decide the focal lenght, based on the desired field-of-view. Also bear in mind that you most likely will continue to use your current scope, unless you sell it. Therefore, it makes little sense to increase the focal lenght just a bit, with a 400mm I'd at least want 600mm, maybe 800mm.

I have a HEQ5 with a SW 200PDS newt witch I use with a DSLR and the finderscope as guidescope. It is heavy for this mount, and as I recently got my hands on a Canon 5D (which adds additional weight) I'm considering a downgrade of the scope. What about a 6" newt, either f/4 or f/5?? SW has their 150PDS (750mm focal lenght) at a reasonable price, and the more pricey 150P f/4 Quattro (with 600mm and a coma corrector). StellaLyra has a 6" f/4 without coma corrector which is priced something between the two SW-scopes.

The SW 130PDS is somewhat hyped, in my opinion, and a bit wee for the HEQ5. The smaller the scope, the more prominent the obstruction caused by the secondary mirror.

Thanks! In my post I said I'm aiming for something in the 750 - 1000mm range, which matches with your advice. The Skywatchers and StellaLyras are possibilities, although I'm a bit wary of the quality given their low price. My current telescope is £1000, the ones you've suggested are half that. I could spend £3000 or thereabouts, so I'd like to get something higher-end if possible. 

2 hours ago, ONIKKINEN said:

Sounds like an 8" newtonian is what you need, although i am not sure if i would recommend one. Depends on how much you want to tinker really.

Ah, this is it, I don't like to tinker at all if I can help it! Hence being drawn to the 107PHQ.

2 hours ago, ONIKKINEN said:

Dont worry about F/ratio in terms of imaging speed, it only affects the length of your subexposure and in your light pollution they will remain short with higher F/ratios. The thing that matters is aperture and working resolution, and if you keep the resolution as same (binning) and increase aperture you get a faster scope. So in reality the F/7 107mm scope will be much faster than your current one (if binned).

I'm not fully clued up on binning... could you explain a bit more? If it only affects the length of my subexposures, then that's no problem. I currently shoot 2-minute subs, it would be easy to switch to 3-minutes. You're saying that if I boost those subframes then I could still aim for 20-hour integrations, rather than the 32-hours I calculated? I'm not sure what's meant by "working resolution". If I bin 2x2, that'll get me SNR faster, but will lower the final resolution? 

2 hours ago, ONIKKINEN said:

If i were you i would go for this premade quality newtonian and add a good focuser and coma corrector on top: https://www.teleskop-express.de/shop/product_info.php/info/p6119_TS-Optics-8--f-4-ONTC-Carbon-Tube-Newtonian-telescope---fully-customizable.html

The price is high but compare it to the 107mm APO and its much more palatable now. I think youll be surprised how much DIY you need to bring a cheap newtonian up to astrograph standards so up to you to figure out whether elbow grease or more spending is the way to go.

This is a possibility, and one I hadn't considered. I'm definitely rather spend a bit more to get something good rather than go down the DIY route.

2 hours ago, Elp said:

A 130pds will be good though your mount could probably handle the larger ones, larger aperture slightly longer focal length and F5. Collimation is also easier, there are other Newtonians to consider, the Orion astrograph being one.

I don't think you'd want to go for a similar f ratio to the one you've already got, you'll get benefit from the aperture which will give you some speed benefit. Having shot with a samyang at f2.8 compared to a vintage lens at f4 and f5.6 you do notice the difference, this is amplified by a scope due to the aperture increase.

Thanks, I hadn't considered Orion astrographs. The AG8 looks very good, although it'd be pushing the budget somewhat 🥴

Hi SGL, I’m hoping to pick your brains…

I’ve been using an Askar FRA400 (f/5.6, 400mm) astrograph for 18 months now, and am having a great time. It’s easy to use, very forgiving, produces good images, and is basically a lot of fun. I’m vacuuming up wide-angle targets and am starting to want something with a longer focal length, say between 750 and 1000mm, basically to get “closer up” to nebulae in particular, which are my favourite targets. I reckon I’ve got another 6 months or so left before I want to make a jump, so am thinking about it now…

I’ve got some criteria for a new telescope:

• Ideally I’d like to keep my existing mount, which is an Orion Sirius EQ-G (very similar to an HEQ5)
• I’d also like to keep and use other existing kit: ASIAIR Plus; ZWO EAF; William Optics 30mm guidescope & ZWO ASI 120MM Mini guidecam; ZWO ASI2600MC-Pro camera with ZWO Filter Drawer, plus Optolong L-eXtreme filter (although I’ll probably buy one of the 3nm dualband filters when they come out)
• The mount is rated for 14kg of imaging kit, but let’s say 10kg to be safe. All those accessories come to just under 2kg. That leaves about 8kg for a telescope plus tube rings etc.
• Budget is up for negotiation, but under £3k would be good

There’s one telescope that jumps out as ticking a lot of my boxes: the Askar 107PHQ. It’s basically a scaled-up version of my beloved Askar FRA400. Good points of the Askar 107PHQ:

• Petzval-like design, meaning no backfocus issues
• 749mm focal length
• 6.9kg including tube rings and dovetail
• Comes with a Vixen dovetail (instead of Losmandy, which my mount would need an adapter for)
• Apparently easy to fit a ZWO EAF
• By my measurements looking at the schematics, an ASIAIR Plus should fit neatly below the OTA, between the tube rings
• £2499

I’m slightly hesitant for one reason: at f/7, it’s a fair bit slower than my f5.6 Askar FRA400. 1.6 times slower, if I’ve understood correctly. I like to rack up long integration times on my targets, currently aiming for a minimum of 20 hours. With an Askar 107PHQ, that would become 32 hours. Ouch. (And that’s good quality data, I normally collect 1/3 more that doesn’t make the cut). There is an optional 0.7x reducer, but that would bring the focal length down to 524mm, as well as requiring a specific backfocus thereby negating a plus point of the Askar 107PHQ’s design.

This brings me to the questions:

• Are there any benefits of f/7 over f/5.6 that might soften the blow of needing longer integration times?
• Should I be considering a different telescope altogether? I’ve always been a refractor guy, but am open to other suggestions. Telescopes like the Sky-Watcher Explorer 190MN DS-PRO, TS-PHOTON 8" f/4, and Vixen R200SS F/4 all have appealing specifications but are beyond the scope of my experience so I'm naturally wary. I worry that they might be a bit fiddly in some way or another, especially coming from the Askar FRA400 that is basically idiot-proof!

Thanks for reading this far. Any help / advice / suggestions / words of wisdom would be appreciated!

-Lee

9 hours ago, Budgie1 said:

I think everyone's workflow may well be different but here's my normal workflow:

1. Crop
2. DBE
3. BackGroundNeutraliation
4. PhotmetricColorCalibration
5. IntegerResample (Bin x2)
6. Stretch with either HistogramTransformation or GeneralisedHyperbolicStretch
7. Starnet 2 or StarXTerminator
8. Curves etc

I do the star removal straight after the stretch so that both stars & background are in the same non-linear state before I start messing with the saturation etc.

Saying this, there's also no reason you can't remove the stars before the stretch because this will allow you to stretch the stars less than the background, so you can control any bloating during the stretch instead of having to do it later or just make the stars less prominent.  

So I guess there's no definite right or wrong answer but I would still do the star removal either right before or straight after the stretch.  

Same here, I remove stars right after the stretch. 

Points for effort! 

I've got quite a powerful computer, but still factor WBPP running for over 20 hours to produce an integrated image. (Mind you, I'm stacking 600+ subframes). 

1 minute ago, Paul M said:

Beautiful image overal but that Soap Bubble is something special.

I researched it last year with plans of having a go myself but never got chance.

Thanks! I spotted it while editing the photo, kinda felt like discovering it 😉

22 minutes ago, simmo39 said:

Nice! I will be getting back on the horse from Aug, Just been brushing the dust off my kit and checking the Askar.

Yes, we need more Askar pics out there!

Hi SGL, presenting my latest OSC from a city centre image: the Crescent Nebula. This is a 25-hour integration taken over three weeks. Lots more details are on my website for those that are interested  

Thanks for looking!

Here's a close crop of the Crescent itself:

And the Soap Bubble Nebula!

* July 2022
* Bristol, UK (Bortle 8 )
* Telescope: Askar FRA400 f/5.6 Quintuplet APO Astrograph
* Camera: ZWO ASI 2600MC-PRO
* Filter: Optolong L-eXtreme
* Mount: Orion Sirius EQ-G
* Guide: William Optics 32mm; ZWO ASI 120MM Mini
* Control: ASIAIR Plus, ZWO EAF
* Software: PixInsight, Photoshop, Lightroom
* 750 x 120 seconds

Total integration time: 25 hours

By Lee Pullen

50 minutes ago, wimvb said:

$T is the image that you apply PixelMath to. It will be replaced. In this case, it is the starless enhanced image.

Copy1 and copy2 don’t need to be stretched as much as the starless, enhanced image. Copy1 will therefore have smaller stars without halos.

You can also create copy1 when the image still is linear and use a colour preserving stretch on it, such as arcsinh stretch. Then create copy2 from copy1 and use starnet on that. It’s all a matter of experimentation.

Thanks, this is really helpful. 

15 minutes ago, wimvb said:

I don’t use starmasks generated by starnet. Instead I first copy the image w stars (copy1), make the original starless and copy that again (copy2). I process the original, and add the stars back in with

$T + copy1 - copy2

This tends to give me slightly better stars in the recombined image than if I use the starmask from starnet.

You've blown my mind, I just tried this and it works. I've finished my Crescent image already, but may use this technique on future images. Two quick questions, if I may:

* What does $T mean? It's selecting the starless image you've been editing?
* How do you go about editing just your starfield? For example, removing halos; adjusting saturation of stars; reducing the number of very faint stars... all the things I currently do to the starmask before putting the stars back in.

Never mind, I've fixed this now. I basically started again! I think the problem was with editing the starless version in Photoshop, and then I must have saved it with the incorrect settings or somesuch.

The two images are attached, in case anyone has time to diagnose where I'm going wrong 😁

v1_NeedsStars.xisf

star_mask1.xisf

13 minutes ago, scotty38 said:

What maths are you using and which images?

PixelMath: "v1_NeedsStars+star_mask1"

I'm hoping someone can help with this issue. I'm probably doing something really dumb, but I can't quite work out what.

So, I've got this starless image:

When I use PixelMath to add the stars back in, the resulting image has different colours:

I've used this technique a lot, and it's never done this. Any idea what I'm doing wrong?

It's worth noting that on the horizon we have 3nm dual narrowband filters coming from Optolong (l-uLtimate) and Askar (ColorMagic). It'll be interesting to see how they perform. 

This Hubble / JWST slider comparison is impressive: https://imgsli.com/MTE2Mjc3

16 minutes ago, ONIKKINEN said:

Thanks, maybe the reason why i feel its not nearly done and i feel mixed about it is how many processing tricks and little adjustments i had to make to make it a presentable image. Processing feels like walking on thin ice, one slip away between way too noisy or the faint outer edges disappearing and that is a telltale sign of not enough integration to pull the detail from.

Also, if you're curious this is what it looked like at 6 hours although i would probably process that image differently if done today, but that's how it goes.

Im sort of extrapolating from that image and this image that around 25 hours would get the result i have in my mind.

Oh yes, I can definitely see the improvement. Roll on 25 hours! 

Looks brilliant to my eyes, I look forward to seeing how it develops with even more integration time. 

That's a great shot, and even more impressive knowing it's just 30 minutes! 

Fantastic, I may have to add this target to my hit list list 🎯

Good job, especially for a first try!