Alkaid

21 hours ago, Alfian said:

Some time ago I bought a Baader fringe killer and it worked pretty well on reducing CA on the luna limb but found the yellow cast distracting. I've just bought a s/h Baader  semi-apo filter to play with so it will be interesting to see how it works out. In all honesty the CA on the Tal100 and the Vixen is not at all bad anyway but the ST120 and the little Optic Star 90  will be a useful test. Will report back when weather plays ball.

Hi Alfian,

That’s great, I’d be really interested to hear your experience with the S/A filter.  For me, it ‘dimmed’ the halo to a darker shade, went from ‘blue’ to ‘navy blue’, still apparent.  But this is interesting, maybe it’s just me as we’re all different and have differing tolerances.

Please would you take the time and effort to advise your findings with all of your Achro’s? That would give a great comparison from another perspective, I’d love to read this if you have the time.

Cheers Steve

Hi everyone,

Had the F5 102 out on Jupiter last night.  Knowing that this would be a tough, perhaps futile test, popped in the Contrast Booster at x100. The planet had a nice tone to it which looked normal to me, fawns and browns etc. After some time and patience whilst the scope acclimatised and detail had to be teased out due to atmospheric dispersion blurring in and out, I picked out the GRS, plus a few other distinct zones.
 

Not bad at all for a little F5 achromat with the planet so low down.  I didn’t bother trying it without the filter, from previous experience the image would have been a mess under these conditions.

Then to Saturn, very small but clear, with a few moons in the vicinity.

Then our own Moon, the brown hue of the CB filter being immediately noticeable, but the image was good.  As it was almost full moon I did not linger, just a quick look.

Liking the CB filter in this scope...

Cheers Steve

32 minutes ago, Philip R said:

How about a 'small' Maksutov or SCT?

The downsides are is...

• the long focal length; (I have an ETX105 and is f/14 or thereabouts).
• dew magnets - a dew shield is a must have accessory and is not included.
• cooling time of thirty minutes [minimum] if used for astronomy; (visual and imaging).
• narrow field of view. (not yet tried with an FF/FR reducer from my C6/SCT-xlt).
• expensive as are dedicated photographic mirror lenses.
• left/right - east/west is reversed.

 

The upsides is that they...

• compact size.
• are excellent lunar and planetary 'scopes.
• hardly require collimation.
• can be attached to photo/video tripod and suitable head. 
• up/down - north/south is right way up.

Phillip, I think the issue with a CAT is narrow FOV.  For terrestrial you really do need a bit of wide field to open up the view I feel.  Whilst a CAT can work well for looking at say a bird, it can take a while to find the bird whilst you’re panning around.  I reckon the refractor would be a better match.  Cheers Steve

You know, if it is predominantly over water as you say, an ED refractor would be better. You’ll be able to push the power a bit without any thermals ruining the image. Perhaps a little 72mm ED or 80mm ED model would be more suitable?

Over water, my short focal ratio achromat starts to produce “poor” images at about x50.  An ED version would go much higher if required.  Don’t forget though that the wide field of view is also desirable and you get that with lower powers.

I use my 102 achromat frequently for terrestrial use.  What I have found is that the best views are over water (no thermals).  You can’t really push high powers for long range terrestrially due to the air currents coming off the land so the achromatic refractor at low power (x20) works quite well, with a wide field of view and is inexpensive.

If anyone suffers from Hayfever, I can attest that it has more than once killed off any early morning summer get ups for me.  If I take a tablet, I'm considerably knocked out during the night and very groggy the next morning (even with the non-drowsy type!).  If I don't take a tablet I'm groggy from the pollen!  🙂   One of my favourite months is September, as then the pollen is gone and I can finally set an alarm and get up to do this.  Keep writing your reports everyone, I really enjoy reading them to see what I've missed!  

Nice!  Looking forward to your Mars reports.  I'm waiting for it too with my C8.

There’s also tracking base mounts for dobs, eliminates the constant nudging.  One of those coupled with the 10” optics would be really good for lunar & planetary at high powers.

On ‎05‎/‎02‎/‎2020 at 00:20, vlaiv said:

Don't use barlow at all,

The best advice.....is just like this.....when you don't have to spend any more money!

Should deliver nice coma free views, the optics will be nice. I think that a lot of the cost went into the ‘light switch’ mount, where it does all the alignment for you.  For that reason it’s aimed at beginners, or experienced visual observers who don’t want the hassle of setting up.  However most experienced observers probably see the mount as a bit of a gimmick and don’t mind spending time on alignment set-up.  They’d rather save some money instead.

If it’s 2nd hand and a good price, it might serve well?

This is a pretty general statement, but on high contrast detailed observing, (think Moon's terminator & crater shadows, Saturns Rings) the central obstruction does not have much effect.   However, on low contrast objects (separating reds and browns on Jupiter, albedo markings on Mars) then the effect of the obstruction really does take hold.  There's a few old threads on this subject and I think that the general consensus was that if you subtract the diameter of the obstruction from the aperture, you end up with an equivalent scope without obstruction.    

For example, my 8" SCT is "very good" (to me!) on the Moon and allows me to see everything that that aperture should, seeing permitted.  But if I then went for Jupiter and started trying to separate the reds and browns, my scope would behave more like this..... 8" aperture minus 2" obstruction = 6" refractor.

It's an interesting subject.

That’s a pretty cool post, I like the pic of the scope and planets in the background.

Hi and welcome! Good news - you most certainly can see galaxies with that scope. You can see M31 (Andromeda Galaxy) quite easily, this was the first galaxy I had seen when I started out and was mesmerised. It will appear as a faint blob generally, but if you get out to a true dark sky site, it is very good.   And...when you’re at the dark site, many other fainter galaxies are well within reach of your scope.  The Virgo galaxy cluster is a cluster of riches. Have fun! (Half the fun is hunting them down).

I can see that with the star de-focused you’ve got nice collimating rings. What’s the pin pointy spot in the middle?  (You normally don’t get that in a de-focused image).  Cheers.

12 hours ago, Highburymark said:

Wouldn’t want to claim anything different - that’s why I said versions available today.

Ah, gotcha - apologies for misunderstanding.

I must admit that I would like to try an Edge someday, but I would love to stretch to the 925 if I could.   It's rather pricey though...🤔

On 14/06/2020 at 15:43, Highburymark said:

There are only two versions available today, the standard C8 and the Edge.

Standard C8s come in black, grey (usually if bought with Evolution mount), or orange (as part of Nexstar SE package).  These are all the same otas.

The C8 Edge has flatter focal plane, vents, mirror clutches etc.

If buying one second hand I’d try and test it first. Some C8s deliver tighter stars than others. 

You’re describing the new ones, all Chinese. Unfortunately the history of the C8 is so varied that it can be rather hard to find out what era an older one came from. Before a certain year, they were made in the US, in all of the colours you mention.

I have a grey one. It has Starbright coatings, these preceded the newer Starbright XLT coatings. The newer XLT’s have a bit more light transmission but it’s a small increase, about 10% or something like that. Would help a little on DSO’s.

I’d say mine was a ‘good’ specimen, views of the Moon at x220 are sharp and ‘hard’ ( no softness in the image).  I pushed it to x480 for fun one night and it ‘just’ (by skin of its teeth) held a reasonably acceptable image.  I don’t have an eyepiece combo that will do a more acceptable x250-300 but I reckon that in good seeing it would deliver.  However, good seeing where live is rare.  x220 is generally the max I go to and the view of a crater like Copernicus is fabulous.  

I haven’t a clue if it’s a US or Chinese one, but I too have not heard of any complaints with the newer Chinese model.

That would be good on an AZ4, I particularly like the same form factor as the 130 with the collapsing tube, great for transporting about.

Really looking forward to your thoughts on this with Lunar high in the sky...very interesting.

That....looks...awesome. I ‘bumped’ into this on Flo’s site earlier today and was quite taken by it. Can’t wait to hear more! Thanks Stu (and Flo).

That’s interesting, if you rack an Achro focuser in one direction (I think it’s inwards) you’ll get the green spectrum. If your condition means that you can’t see green, then you might not be seeing as much CA.  I had a TAL100RS that when in focus exhibited it’s false colour in the green spectrum rather than blue. 

Weirdly, for me the SA filter just ‘dimmed’ the CA. It did make it less noticeable but to me, absolutely consciously looking for it, it was still there and more so than with the other filters.  I think that is a good point though regarding sensitivity.

Welcome to the club!  

2 hours ago, Mark at Beaufort said:

Steve that is a very good report on these filters. I enjoyed the read and your conclusions. I assume that someone with a 120mm or 150mm Achro, having gained more light, should consider the contrast booster above the others.

Thanks Mark, yes indeed - I think that with the larger aperture achro's the contrast booster would be a solid performer.  I'd like to try one with a 150mm F8 someday. 

11 hours ago, John said:

Very good report and comparison Steve

 

Thanks John, I've had this in mind for some time.  Realised that I couldn't really review just the one.....I'd have to get all three!