Living life on the Edge......

[Stu]

I'm blown away by the capabilities of those WR's. I remember thinking at SGLX it doesn't look up to holding much due to it's compact size yet it was as if the scopes were floating on air. I had tried to get my hands on one a while back to replace my AZ3 but the smaller mini seems to come up more often on the used market. I settled for an AZ4 on steel tripod in the end. Can't fault the AZ4 though but would still be nice to have a compact twin view like the WR.

Thanks Nick. Yes, I agree, they are pretty amazing for something which weighs under a kilo! Very capable with a single light scope, but can take quite a lot when properly balanced. Actually the weak point is normally the tripod which is why I stick mine on an EQ6, really solid then and barely any vibration. The tensioning is nice and progressive too

[nightfisher]

8 is fine. We won't tell anybody

And there is little ol me with four, and still wanting to get back to just one scope  

[Stu]

And there is little ol me with four, and still wanting to get back to just one scope

You'll never do it Jules , not for long anyway.

[Tim99]

Nice.  Really NICE!  I am considering an Edge 9.25 at this very moment.  From what I have read, people seem to think these scopes are very nice.  I will be interested in your report on your new Edge.

[jetstream]

Great choice Stu! That scope is gonna perform...

[damnut]

Nice addition to your arsenal Stu. Would look great on a skytee, big frac on the other side,baby apo in the middle for a finder. It will definitely take it as I have had a 10" SNT at one end ....

[Stu]

I managed a bit of a session with these two yesterday night, although I was battling patchy cloud and high haze!

I only ended up looking at the Moon, Saturn, M57, Izar and the Double Double.

It was interesting to see the differences quite clearly, and exactly as I would expect.

The Edge has a central obstruction of 34% by diameter or 11.5% by area. Despite this it still has quite a substantial overall area advantage of 28626 mm2 vs 17671 mm2 for the frac. I tweaked the collimation on the Edge whilst looking at Vega, and it looks pretty good.

I was not particularly keen on the image shift which, although not too bad, still makes focusing trickier than necessary. I'll most likely invest in a focuser for it at some stage.

On the moon, the image in the Edge was brighter, showed slightly better resolution but had less contrast. I mainly looked at the crater Theophilus which was nicely illuminated. The central twin peaks were showing nicely, as was some detail in the crater wall despite it still being quite light. Overall there was not much to choose between the views, although had I jacked the magnification up or it had been darker then things may have been different.

Saturn was not looking brilliant in either scope, although it was better in the Vixen. The contrast was again better, A, B & C rings visible and also Cassini when the seeing allowed, the SCT did not show as much detail on this and was probably more affected by the seeing down low.

I was generally quite pleased with the star shapes in the Edge, they were better than I was expecting, although still lacking the beautiful diffraction ring and central airy disk of the refractor. This showed most obviously on the Double Double. The Vixen has recently had its collimation tweaked, and it really showed. The Double Double looked as good as I've seen it, lovely and crisp, with 'huge' separation between the close pairs. Really nice. The Edge split it too with no problem, but was lacking the crispness of the frac, the separation less clear.

Izar was another similar story, beautiful, crisp stars with clear separation in the frac, 'fuzzy' stars with barely any separation in the Edge, although the split was still obvious, as were the star colours.

Now, I'm totally open to input from experienced SCT owners as to anything I may not be getting right. I suspect the main thing may just be thermal equilibrium and tube currents. It was a warm evening, so it's quite possible that the sun was on the scope for a little while, although the same applies to the frac. I shall persevere with it and report back again.

The scope has passive vents in it at the rear, I'm not sure whether a cooling fan in the visual back would help to pull the hot air out of the central baffle and help the cooling. Perhaps?

So, the first minor skirmish between the two. Nothing conclusive to say, other than I'm basically very pleased with the scope. I've just bought a Geoptik bag for it to make it easier to transport, and as an option for getting a little bit more aperture somewhere dark it will be hard to beat. Actually with the FC-100 and this on my Giro-WR in the depths of Dorset or Exmoor even, I should be pretty sorted!!

[philj]

Nice one Stu,

I did something similar a few years back with my old C11 and my 127EDT on my Giro 11 mount but I only tried it for the sake of it. It wasn't really practical.

[Stu]

Nice one Stu,

I did something similar a few years back with my old C11 and my 127EDT on my Giro 11 mount but I only tried it for the sake of it. It wasn't really practical.

How did you find the comparison Phil?

[philj]

I bought the 127 because I was going more refractor and the c11 had hardly been used for ages. I decided if I liked the 127 I woukd sell the c11. The c11 was sold shortly after:')

Ok the c11 had the apeture hut the apo was far sharper and contrasty. Ive never regretted selling the c11. Ok 127 is limited on faint dso compared to the 11" but I could still see the veil in the 127 and m13 was still spectacular.

[YKSE]

Nice first light, Stu.

Some of my thoughts:

1. Vixen should do somewhat better than C8 for the targets you've chosen, especial for the doubles, because these are bright ones, the aperture advantage of the C8 can be disadvantage in regard of seeings.

2. Thermal balance can be an issue for C8 as you suspected, I've noticed that stars are noticeable tighter late in a session(2-3hours later) than in the begining (a couple of hours cooling already).

3. Collimation. How stable was seeing when you collimated on Vega? Could you go higher than 400x, and still see complete diffraction rings with Vega very slightly defocused? Sometimes, the seeing's not so good for a better collimation, and good collimation is essential for SCT to perform.

[Stu]

Nice first light, Stu.

Some of my thoughts:

1. Vixen should do somewhat better than C8 for the targets you've chosen, especial for the doubles, because these are bright ones, the aperture advantage of the C8 can be disadvantage in regard of seeings.

2. Thermal balance can be an issue for C8 as you suspected, I've noticed that stars are noticeable tighter late in a session(2-3hours later) than in the begining (a couple of hours cooling already).

3. Collimation. How stable was seeing when you collimated on Vega? Could you go higher than 400x, and still see complete diffraction rings with Vega very slightly defocused? Sometimes, the seeing's not so good for a better collimation, and good collimation is essential for SCT to perform.

Thanks Yong, very useful info.

You are correct of course, I did not buy the scope for double star work, and there are plenty of targets where the extra aperture will make a difference. I was somewhat limited in time and available targets in my session.

I should also note that any comparison is purely for interest sake. I got the Edge for very different reasons that the Vixen so it's fairly academic.

Thermal equilibrium is the one thing I've been concerned about. It's interesting that you notice a difference over such a long period. Looking back I don't think I ever got the cooling properly sorted with my Mak, so will make sure I understand this scope better.

The seeing was not particularly good, and I did not take the magnification up beyond around x200 so will give the collimation more attention next time. I do also have an artificial star I could use, so might give that a go too.

Thanks for your help!

Stu

[Tim99]

Very nice set-up.  I love that comment about getting a telescope for each month of the year.  haha.  I seem to be on my way with that too ... just ordered another telescope.  That makes 4 scopes now.  I just ordered the 9.25.  Spent a bundle with the CGEM mount package.  Can't wait to see what it can see.   LOL

[Mrbloke]

Nice setup, its almost like a pair of AA guns!

[John]

Very interesting report Stu

One thing I've found lately on Saturn is that my ED120 is throwing up a nicer image most of the time than my 12" dob does. Last time around, when Saturn was higher in the sky, it was the other way around and the dob would beat the 120 most of the time. I put the reversal in observing performance on Saturn down to it's low altitude and that the refractor "cuts through" the negative effect this has better than the larger aperture scope. Maybe this effect was hampering the the Edge ?

I had some of my best views of Saturn through a well collimated C8 SCT a few years ago when Saturn was much higher in the sky. The collimation did need to be spot on though. A small amount off and the contrast and sharpness reduced quite noticably. I could never quite get star images that matched refractors through the SCT's that I've owned even when they were collimated really well.

I feel that scope designs with proportionately large central obstructions can perform excellently when well collimated but the drop off when thats not quite the case is rapid and rather unforgiving.

[Stu]

Very interesting report Stu

One thing I've found lately on Saturn is that my ED120 is throwing up a nicer image most of the time than my 12" dob does. Last time around, when Saturn was higher in the sky, it was the other way around and the dob would beat the 120 most of the time. I put the reversal in observing performance on Saturn down to it's low altitude and that the refractor "cuts through" the negative effect this has better than the larger aperture scope. Maybe this effect was hampering the the Edge ?

I had some of my best views of Saturn through a well collimated C8 SCT a few years ago when Saturn was much higher in the sky. The collimation did need to be spot on though. A small amount off and the contrast and sharpness reduced quite noticably. I could never quite get star images that matched refractors through the SCT's that I've owned even when they were collimated really well.

I feel that scope designs with proportionately large central obstructions can perform excellently when well collimated but the drop off when thats not quite the case is rapid and rather unforgiving.

I think you are right John, Saturn is quite frustrating at the moment and the smaller scopes do seem to cope with the seeing better.

I would be interested in understanding the best way of collimating the SCT. I'm assuming a star test or artificial star, but are there any other methods? Will have a search around anyway.

I suspect locking the mirror at a mid point and using a focuser on the visual back may well help with collimating too? Mirror shift must have some affect?

[DRT]

Believe it or not John I'm trying to slim it down a bit!

8 now, 5 fracs, the SCT and two dobs! That's it, no more...... Am I sounding like Derek?

Oi !!

I'll have you know I have absolutely no plans to sell any scopes this month 

Nice scope, Stu. As you know I have a CPC1100 and until a few months ago had a C6. I found with both of these that they performed much better in winter than in summer, so much so that the CPC hasn't been out its box since SGLX. Whether that is down to thermal currents in the OTA or simply a lack of contrast under bright skies I'm not sure but I strongly suspect your 8" Edge will come into its own in two or three months from now when you can point it at a dark sky. If the CPC1100 is anything to go by Jupiter and globs should be fabulous targets with your new scope and should take a good amount of magnification.

[John]

I would be interested in understanding the best way of collimating the SCT. I'm assuming a star test or artificial star, but are there any other methods? Will have a search around anyway.

I suspect locking the mirror at a mid point and using a focuser on the visual back may well help with collimating too? Mirror shift must have some affect?

I used to use star testing to collimate mine. I had "Bobs Knobs" fitted to the ones that I've owned but some folks don't like those.

Some useful stuff here but I don't know if Edge SCT's are any different ?:

http://www.sctscopes.net/SCT_Tips/Maintenance/Collimation/collimation.html

I used to get a bit of "mirror flop" if the scope crossed from one side of the sky to the other, as the mirror shifted slightly. That was quite frustrating

[Stu]

I used to use star testing to collimate mine. I had "Bobs Knobs" fitted to the ones that I've owned but some folks don't like those.

Some useful stuff here but I don't know if Edge SCT's are any different ?:

http://www.sctscopes.net/SCT_Tips/Maintenance/Collimation/collimation.html

I used to get a bit of "mirror flop" if the scope crossed from one side of the sky to the other, as the mirror shifted slightly. That was quite frustrating

Brilliant, thanks John. The Thierry Legault link is excellent, just what I need. I didn't realise quite how sensitive they were!!

I have Bob's knobs fitted so that makes life easier.

Cheers

Stu

[Stu]

A couple of developments to update on this thread.

Firstly, although I have been considering a FeatherTouch focuser, I happened upon a nice Baader SteelTrack with SteelDrive for less money and have now fitted that. It makes a big difference, I lock the mirror and am them able to fine focus without causing any vibrations and with no image shift at all.

I've also been away in Devon for a week, and have been able to give it a good run out under some dark skies. I'll report on this in detail in a separate report, but suffice to say I'm delighted with the scope.

I think I've now found my ideal UK holiday setup. The EQ6 tripod, my home made pillar for extra height and the Giro-WR head.

With dual clamps, I can mount the Edge plus the Tak FC-100 together and have aperture plus wide field capabilities together. The Tak in effect becomes a mega finder for the SCT!

Since I am camping, I have been able to properly cool the scope down, and this has made a difference to the sharpness of the stars; they are tighter when cooling is correct. With a 21 Ethos in the diagonal, I get around 1 degree of sky, and the stars are very sharp right to the edge, so the improved optics definitely seem to have something to offer.

I had cracking views of the Veil through it, bright and with lovely detail showing through.

Planetary performance, well Saturn at least was reasonably good, not as sharp as the Tak but that is probably due to the poorer seeing conditions down low. It is capable on doubles, but probably needs to be mounted on the AZEQ6 for this so that I can chuck plenty of power at them to split the closer ones.

A great addition to my stable, and one which I think will be around for sometime.

I'll stick on 8 for the moment.

[YKSE]

Nice to see someone is satified.

[Luke]

Nice one, Stu! I am hoping to take my Edge 8 to Dorset later this year. I hope it can fill in as a mini light bucket seeing as the Mrs doesn't feel we can squeeze a 16 inch dob in on a regular holiay    

I really like mine for lunar too, it gives me a nice step up in detail at higher mag than my 120mm frac

[Stu]

Well worth it Luke, I was really impressed with it. Nice to have a bit of aperture with me for a change . The combo with the frac was great