Another newbie looking for advice.

[Andy56]

Hi,

I've just got back into astronomy in practical way. I was fortunate to get a Star Adventurer as a retirement present  some 5 months ago. Up to now I've been using it with a Cannon 600D an some old Pentax zoom lenses (70's). I also bought a Carl Zeiss Jenna 135mm. Both of these give coma and the infamous purple star bloat.  I don't have any modern lenses. I bought the 600D as body only.

15 darks, 42 subs, no light frames, ISO600 F3.5 Carl Zeiss Jenna 135. Bortle 6ish or higher. I've stretched and played with it in Gimp. It looks like it needs some light frames.

So I want to upgrade to a small telescope so I don't have to fight lens quality as well as all the other new tasks laid before me when starting with astrophotograhy.

My interest is mainly nebula and using Astronomytools around 400mm is what I will need.

Looking through this forum I find two candidates William Optics Zenithstar 91 FPL53 and Skywatcher 72ED-pro. These are about the right focal length, f number and weight. The SW is significantly cheaper than the WO, probably a guide scopes worth.

Looking through astrobin, both seems to give excellent results but there is no mention of how much processing was used. I realise that some star bloat can be removed by masking.

I was leaning towards the Skywatcher but then I've just read this thread that seems to imply the Skywatcher has CA.

So after nearly making up my mind all is in doubt.

So do you good people have any suggestion as to which to go for and are there any other suggestions?

Many thanks

Andy.

 

 

 

[Clarkey]

Hi and welcome to the forum.

Both the WO and the SW are doublets so are potentially going to give some CA (I assume you mean the 61?). I think in general terms you are paying extra for the mechanical qualities of the Zenithstar which is undoubtedly better than the SW. Having said that, I have an ED80, the slightly bigger brother of the 72 and the image quality is pretty good. The only way you are going to get a major improvement is to look at triplets - but there is a significant cost increase.

Both scopes will need similar amounts of processing - so I would not use this as too much of a guide. If your budget is tight the SW 72ED will give pretty good results, an as you say the difference will pay for a guide scope at least. For my ED80 I use the SW 9x50 finder with a C adaptor to guide.  At 180mm focal length it is fine. FLO do it as a package:

Sky-Watcher 9x50 Finder & ZWO ASI120MM-Mini Bundle | First Light Optics

 

[Merlin]

That’s a very nice image of the Orion region.

[The Lazy Astronomer]

You're going to have some level of bloat in the blue channel with all doublets. It can be reduced quite significantly by using a filter which cuts the blue end of the spectrum at around 400 - 420nm - the Astronomik L3 filter works well in this regard. 

[AstroNebulee]

That's a lovely image of Orion there, you've got the flame and Horsehead nebula in there. Keep going your doing great 👍

Edited February 20, 2021 by LeeHore7
Spelling again

[callisto]

That's not bad at all 

[alacant]

20 hours ago, Andy56 said:

Carl Zeiss Jenna 135mm. Both of these give coma and the infamous purple star bloat.

Hi

Lovely shot.

Strange about the halos. We find it one of the few colour free old lenses. Maybe it drifted out of focus a little? This is the same lens around f5. With a UHC, it should really pop.

If you want to get closer, here's another example of the same region with a 200mm Takumar.

Closer still, there's the Russian Tair-3 at 300mm. A 72mm triplet for €60.

Choose a bright star. In the Zeiss, mean rgb focus is a tiny turn away from the physical infinity. You'll see the halos around the star change colour.

Bear in mind however that old lenses give nowhere near the definition of their modern counterparts or telescopes designed specifically for astrophotography. They are however cheap and more importantly, available now.

Cheers and HTH

Edited February 21, 2021 by alacant

[Andy56]

LeeHore7 and Callisto: Many thanks to your comments and complements. I do like the pics overall but the coma a CA put me off.

Clarkey: Thanks for the heads up on the finder/guider bundle that should allow longer exposure if my skies allow it. Mind you lockdown eases I can get up to the hills where it's much darker.

The Lazy Astronomer: I may get an L1  filter if I have issues. Looking at other's example I may not need it.

Alicante: It may be a poor lens because as I remember the East German lenses could be a little unpredictable.  I had a Zenith once which gave excellent pictures. In terms of focus the Pentax lenses are on a PK mount adaptor and at their focus limit. The Carl Zeiss can go just beyond infinity. I'll try it at F5, I had a CLS filter in at the time.  I have other Pentax lenses eg 35mm, 50mm and these show coma on two cameras so at the moment I'm not to impressed with the old lenses I have. Your experience gives me hope. Stopping down the Pentax 210mm zoom from F4 to F8 made a considerable difference to the CA but still loads of coma. Regarding using old lenses I'd rather buy something with new technology now, while I have the cash, so I can get started without to much disappointment . This will also give me a longer focal length which I'm after.

From this and further reading I think the WOZ61 is the best option being a doublet of FPL53 (at least one element) and lighter and possibly get the finder/guider bundle and while I'm waiting for these I'll try some more with the lenses I have, weather permitting.

Kind regards

Andy

[Newforestgimp]

Moving from vintage lenses to a WO ZS61 myself I was amazed at the improvement, but you will need the Field Flattener, so factor that into your decision. I went for the WO Flat 61A just so I knew it would all work together and its genius, Round stars right to the edge of frame. I tried without flattener and couldn't live with the results it was too restrictive to crop the image down to remove the stretched stars.

Nice Pic BTW 

[Andy56]

Update:

I've ordered a WO61 + fittings, OVL flattener and guide scope from FLO. 'Scope's in stock but there be a wait for the rest. 

Alicante: Tried the Zeiss at f8, much better on the colour but still more coma than I would like. 

 

Cheers

Andy

[Spaced Out]

Great image, the star adventurer does it again ! You can see the flame and horsehead coming through there too.

I hope you don't mind, I chucked your image through Lightroom to try and remove the purple halos a bit, it's not perfect but there is less purple.

 

[Andy56]

Hi Spaced Out,

I have no problems if you can improve my photos, it shows me what can be done. I can give you the subs if you like. It will show me what can be done with an expert on the job and give me hope. I know there's a lot te learn.

Currently I use DSS, Sequator and Gimp. I have no access to Adobe products except Photoshop Elements 2020.

I have taken some more shots over the last weekend at F8 with an Optolong CLS filter.

I took the time to ensure the focus gave the least colour on the stars at F3.5 and then stopped down. The problem I have with these images is that the moon and the light pollution (LED lights) bleached out everything beyond my ability to recover the details.

I have taken flats as well to remove some of the vignetting.

The ZO 61 plus flattener arrives today. I'll be using this asap but of course there won't be any clear nights for ages now even as the moon wanes.

Regards

Andy

[Clarkey]

I'm not sure how you find Gimp, personally I did not really get on with it. I purchased Affinity Photo which I find excellent. At the moment it is 50% off at 24 pounds which is a months rental of PS. Also, the developers seem to be getting on the AP bandwagon and are starting to add useful tools. There are also some macros available from James Ritson which can help.

[Cobberwebb]

In my short experience shooting with a SA and Nikon Z50 with the 50-250mm kit lens, flats are more important than darks. In fact I've stopped doing dark frames altogether and I've been getting great results.
I'm looking to get the WO ZS61, so hopefully that will be a improvement over the kit zoom lens.
 

[Andy56]

Clarkey: I have only tried GIMP so I can't compare. But it's like any other tool you have to read and try. I have found it very usable so far but some of the PS Youtube videos I've seen make PS easier to use. But then I've not looked for those features on GIMP.

Cobberwebb: Nice picture. You seem to have smoother detail than me, but that could be the awful light pollution in my area. I'm finding it difficult to separate back ground noise/pollution from the nebulosity. What's the Bortle number for where you took this, it's supposedly 5 in my area but 6 is more likely given the number of street lights in the area and Newbury is to the South. Can't wait for the lockdown to be lifted so I can go to better site. I use darks because I bought a second hand Canon 600D and it has some hot pixels. The darks remove them completely.  I don' have any modern kit lenses for the Canon but the WO ZS61 meets my expectations.

 

 

[happy-kat]

I've found sequator made the CA worse when I was using data from a CA prone lens. I use DSS but I gather the are some good noise tools in SIRIL which is another free stacking option you might like to look at.

A sub is a light frame. Different name but the same thing.

For noise I've found dark flats help, and they are easy to take seeing as you're taking flats. Same as a flat but with lens cap on.