6" f8 Helios comin along nicely...

[A McEwan]

Hi all,

Inspired by Dave's project 6" f8 achro, I'm getting on well with my own upgrades to my newly acquired one. It's been completely disassembled and stripped (had to get the paint shot-blasted off in the end, it was completely resistant to paint strippers!)

It's taking a lot of layers to build up the colour (Ivory) too so it's quite labour-intensive. The weather isn't helping, either blustery or wet so far with only one sunny calm day.

The new GSO Linear focuser arrived today, and I'd finished and lacquered the finderscope so here is the rear end all reassembled and ready to put on. The focuser works very smoothly and will be a big improvement on the rack & pinion. It will also allow enough in-focus to use my Herschel Wedge with all (or most, at least) of my eyepieces.

Ant

[spaceboy]

You have me intrigued Ant. I see from your sig that you have a moonlighted E120 but you are splashing time & cash on a 6" achro. Would this suggest that the Evo150's are something special. I was told by a supplier that CA increases with aperture and that given they need a substantial mount the 120mm would be a good compromise. Having read Dave's 1st light and seeing that good money is being spent on these scope I can help but have my curiosity aroused. I have found that when my Evo120 is well collimated the lens is clean and the tubes temperature is equal to the surroundings CA isn't actually that bad so I guess this is also true with the 150 ????

[A McEwan]

Well, Spaceboy, I don't see the 150 achro as a competitor to the ED120. The ED120 should have the edge in planetary viewing as the CA will never be an issue. CA is not just a visual annoyance - it also blurs the fine detail that planetary observers look for.

That said, I'm going to be using a fine CA correction filter with the 150, which should reduce it by a large amount, making the view on bright objects, aesthetically at least, much better. Primarily I see the 150 achro as an obstructionless 6" light bucket for DSO's, globs, open clusters, nebulae etc, using moderate powers - but with the oomph to go higher and deeper on planets sometimes when required. Also, the GP mount I use carries it well enough, so no need for a heavier mount for me!

Re the CA on a 150 f8 vs a 120 f8.83 achro, side by side the 150 will show more false colour - that's to do with the CA index, which is basically a scale of how high the f-ratio has to be to present an acceptable level of CA. At 120mm f8.83 is ok, but at 150mm f8 is "less ok" than the 120, if you see what I mean. But then CA isn't noticeable on deep sky objects, and some people are more sensitivie to it than others.

Personally, I just love using refractors, so am willing to give it a fair shot!

Ant

[John]

Logic goes out of the window a bit where big achromat refractors are concerned. They don't really make sense in many ways but are loads of fun to own and use - plus they look like a telescope should look

[spaceboy]

I do like my EVO120 but brand new out of a shop I'm sorry but I would have to go with the Explorer 200P. I can understand people wanting apochromatics as you get your cake and eat it but I naturally thought it stopped there. I realize what you are saying about the 150 for DSO's but £500 of the shelf would get you some aperture in a reflector. I agree in the S/H scenario you can't go far wrong as achros seem to go for pennies where a similar sized reflectors hold there value well in comparison. I guess when I think of it this way I can see the appeal. I just never thought an owner of an ED of near similar size would find an achro appealing.

I hope someone is going to PSP with one of these as I would love to have a look through one and I'm sure I would understand the allure of a big frak.

Thanks for the info Ant I have found it very interesting.

Look forward to seeing the finished scope.

SPACEBOY

[A McEwan]

Ok, Spaceboy - you've opened up some more cans there!

An Explorer 200 tube is a lot of light gathering, but (as an 8" Dob owner) the view through a refractor (apo or achro) is different. Also I can't stand equatorially mounted Newtonians - the eyepiece goes every which way, meaning rotating the tube (at risk of misaligning the scope and/or mount) and risking it sliding back "down" the mountin rings. Been there, done that, had the therapy.

The 150 acho will be equatorially mounted and will work easily, never needin to be adjusted once it's balanced. Ok, the eyepiece might get a bit low when pointing straight up, but to be honest that doesn't happen that often.

Also, 120mm is not similar aperture as 150mm. 30mm difference may not sound like much, but bear in mind that those extra 30mm are at the outside edge of the 120mm, and thus represent a great increase in surface area and therefor light-gathering ability.

Using a Herschel Wedge for solar viewing, as I do, my 120mm shows more detail than my 90mm. The 150mm shows more detail than the 120mm. As my wedge has a Baader Solr Continuum filter pernanently installed which blocks nearly all evidence of unfocused light, CA is simply not an issue for me when viewing the Sun through this behemoth!

And finally... maybe you've got to stand beside one to appreciate one, I think!

And finally finally... as you pointed out, these are going very reasonably second-hand. As an owner of a 120ED I didn't mind the asking price for this scope. If I didn't already have a large Apo I wouldn't have gone for the 150 achro first - I'd have gone for a mid-aperture apo - which is what I actually did!

Ant

[nightfisher]

I do like my EVO120 but brand new out of a shop I'm sorry but I would have to go with the Explorer 200P. I can understand people wanting apochromatics as you get your cake and eat it but I naturally thought it stopped there. I realize what you are saying about the 150 for DSO's but £500 of the shelf would get you some aperture in a reflector. I agree in the S/H scenario you can't go far wrong as achros seem to go for pennies where a similar sized reflectors hold there value well in comparison. I guess when I think of it this way I can see the appeal. I just never thought an owner of an ED of near similar size would find an achro appealing.

I hope someone is going to PSP with one of these as I would love to have a look through one and I'm sure I would understand the allure of a big frak.

Thanks for the info Ant I have found it very interesting.

Look forward to seeing the finished scope.

SPACEBOY

I will have my 6" frac at psp but its the f5 version, what your saying about a big reflector also makes a lot of sense, a 200 should be as good or even better, i guess!

ant your making real good progress keep at it, so much nicer than a cheesy carbon wrap, i might still go for white paint on my f5......i can get it done foc:D

[A McEwan]

FOC? Lucky you! I'm a bit more confident now I've seen the finder done, and I'm finishing the dewshield this evening.

Spaceboy, I forgot to say thanks for your interest and thought-provoking questions! Keep em coming

Ant

[nightfisher]

FOC? Lucky you! I'm a bit more confident now I've seen the finder done, and I'm finishing the dewshield this evening.

Spaceboy, I forgot to say thanks for your interest and thought-provoking questions! Keep em coming

Ant

Im lucky, the company i work for spend about £5000 per week on paint spraying, and the contractor will slip a scope tube in foc

[F15Rules]

Ant,

It's looking really good, you should take this up full time:p. Seriously, I love the look of that "rear end"..

I think Spaceboy's interesting responses demonstrate quite well the differences in how we all look at different scopes - and all views are of course completely as valid as any other..it's just what floats your boat at the end of the day.

I'll pin my colurs to Ant's mast..I just like refractors. I dislike reflectors for all the reasons Ant mentions, plus the way they crick my neck when trying to use the finder:eek:..

I like to sit "behind" the scope, and in a frac (and a Mak) you can do that. They are low maintenance and deliver razor sharp images..and a good achro can deliver images just as sharp as an apo, but with a smidgeon of colour - at a fraction of the cost.

I would say that a 120 at F8.3 and a 150 at F8 will show similar amounts of ca..in fact I've heard it said that some SW 120's show more than the F8, but I can't say that from direct experience. To get ca really down in an achromat you'd need to go to around F15 and ideally to F20:eek:, by which time you'd need a winch and a crane to use it! So the F8 is a good compromise on aperture vs CA and below about mag 1.5 you really don't notice it.

It's a great debate though and I don't doubt that a view of DSO's through a real light bucket newt or dob at 10" and higher at a dark site must be a sight to behold!

Good luck with the upgrade Ant, and don't forget that first light report;)

cheers

Dave

[nightfisher]

just to throw a quick question.........i have heard of people using a chair to observe with fracs on eq mount, now im a frac fan and always stand to view, maybe i should get my fishing chair out and give it a whirl?

[spaceboy]

Spaceboy, I forgot to say thanks for your interest and thought-provoking questions! Keep em coming

Ant

No Thank you Ant! I have asked the refractor vs reflector question as so many others have but found that all it dose is bring the fans of each in to a head to head an no real understanding is gained. I tried asking the question in a less obviously way http://stargazerslounge.com/astro-lounge/129863-who-has-what-refractor-reflector-both.html and avoided the usual debates. This resulted in me purchasing my first ever refractor as I was able to see the refractor design clearly had it's followers. I may have a refractor now but it doesn't mean I have got my head around it all yet. I guess the whole achro, apochro' thing isn't helping either but your replies are helping to see the bigger picture. I suppose another thing that has to be considered is price. I wonder is refractors were as affordable as reflectors what the most commonly sold scope would be. I'm thinking refractor fans are people who have a bit of poke behind them that they have had the opportunity to see the benefits in refractors where more often reflectors are purchased by astronomers on a budget that are looking to get the best bang for their buck ????? I sure know if I had the ££££'s I would like the chance to have a 120ED myself. Dose any of this make sense

[A McEwan]

Thanks Dave. Of course in a refractor the objective is higher off the ground too - better for avoiding thermal currents...

"All things being equal" is tricky, as some nights the seeing may be just not good enough that the smaller refractor gives a sharper clearer image than a larger Newt - no matter what the difference in aperture or quality.

Right, I'll be very careful not to venture down the refractor vs reflector path now...

But certainly I see a "big" refractor complementing a "medium" refractor, no matter whether they are achro's or apo's.

Fisher, I always sit to observe, no matter what I'm observing or what I'm observing with. Less wobble = better views = more detail = more reward.

Also, Spaceboy might notice that I have a Newt as well and have owned several Maksutovs in the past too. I may well own another one at some point. All scopes are worthy scopes as long as they're looked after and used and enjoyed. There are some slight differences between them, for sure - but not as big as the difference between observing and not observing!

Ant

[spaceboy]

If there is one thing we are agreed on that is reflectors and EQ mounts are a pain. I am seriously considering giving up my CG5-GT for a Skytee and going through the old games of finding DSO's washed out by LP.

[SpookyKatt]

Looks nice so far Antony, that new focuser looks great

but the picture doesn't really betray how big it will

be hehe.

The best thing I bought for using a big refractor on

an EQ mount was the pillar extension, it made such

a difference, not having to stoop anymore.

Looking forward to seeing the finished article.

Kathleen

[A McEwan]

Hmmm.... a pillar extension... handy thing! There was a recent post over on CN about using two diagonals for when observing objects high in the sky. Stick a second diagonal into the first one and orient it so that it's pointing upwards to make viewing easier! Depends on whether there's enough in/out-focus to do that of course...

Yes, Kat - it will be big (but no bigger than it was before! LOL)

Ant

[John]

I found a 16" pillar extension exceptionally useful when using big refractors. I have the Orion (US) version which can be bought new from the Widescreen Centre for £89 plus some P&P I expect as it weighs quite a bit !.

Well made piece of kit though and got the eyepiece of my Meade AR6 over 5 feet high even when viewing the zenith area. Impressed the neighbours as well as it put the total height of the scope (to the top of the dew shield) at around 9 feet

[SpookyKatt]

Yeah the pillar extension certainly helps the big

refractors 'reach for the stars' if you'll parden the pun

and make a big setup even bigger. But there's nothing like

being able to carry out polar alignment standing upright

hehe.

Never heard that about the two diaganols Antony, I'd

be worried about loosening the wrong screw with that

setup though and dropping it all onto the flloor.

Kathleen

[A McEwan]

Don't know if this link will work, but here goes: Telescope Reviews: Lot’s o’Back Focus

It's in the Refractors forum under "Lot's o' back focus".

Looks neat but I've never tried it myself yet. Yes, stuff does tend to give way to gravity at the most inopportune moments, usually with expensive sounds accompanying them...

Ant

[F15Rules]

I always prefer to sit when I can. You feel more comfortable and it's much easier to keep your head rigid which is important to see fine details.

Of course, if you flit from object to object very quickly, and to all parts of the sky, you will end up moving your chair around a lot, and that's where it gets complicated, as your chair will be ideal height for some objects, not for others...unless you have a proper astro chair (I feel a Christmas wish list starting...).

I actually use two chairs...one is a simple garden plastic chair, very lightweight (in the winter I put an old cushion on it), and I also use a tall kitchen "bar stool" type seat..that is great for looking at things lower down in the sky where the eq mount is pointing at a much shallower angle...the ep end is therefore higher off the ground and often too high for the garden chair...the bar stool is taller and has a footrest ring about 6" from the ground so you can brace your feet on it and get quite comfortable.

I've not had a proper observing chair before, what do you guys think of them and are they worth the money?

Dave

[A McEwan]

A teaser pic for you all...

Paint is on, lettering is on, just a final coat of lacquer to go, then some curing and then some waiting for first light! Very pleased but you aint getting to see the whole thing until it's fully finished...

Ant

[nightfisher]

Ant, im so glad you stuck with it rather than the option you asked me about, that sneaky teaser looks very good indeed, you will have the pleasure of using a custom frac that is a real beauty, cant wait for proper pics...

[SpookyKatt]

Ooooh that teaser looks really good Ant, I'm looking forward

to seeing the finished scope...

Kathleen

[spaceboy]

Awww you big tease

[A McEwan]

Nightfisher: me too!

Kat: Not long now... hopefully!

Spaceboy: ... yup!