#21  
Old 04-05-2019, 05:57 PM
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Merlin66 (Ken)
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Hemi,
If youíre serious about building a 6Ē I have a very good 6Ē mirror and a diagonal and focuser just needing a tube and assembly.
Drop me a PM if youíre interested.
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  #22  
Old 04-05-2019, 06:10 PM
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Outcast (Carlton)
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Quote:
Originally Posted by Hemi View Post
I should stress again that itís going to take some tectonics to shift my 925 off the mount.
I can completely understand why mate... the wow factor of an 8" SCT is pretty damn good... 9.25" would be a step up again...
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  #23  
Old 06-05-2019, 10:20 AM
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sil (Steve)
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Quote:
Originally Posted by mental4astro View Post
The BEST scope is the one that gets used.
Spot on right there.

If you want to know the horrors of a manual EQ mount with a Newt then go for it. Its what newbies see as being a typical telescope and they can be impressively large for little cost. So its a con and people quickly find its a poor choice and get put off as a result. Refractors, Newtonians, Dosbonians and Cats all have there place in astronomy for various reasons, Hense they are commonly found. Learn what the figures actually mean and what the strengths and weaknesses of each type are and you start to understand why there are choices and why no single type rules them all. They each rule something. If you have scopes that do what you need then thats all that matters. Collimation isn't too difficult, again learn what the adjustments do . I think most problems people really have with newts is down to the tripod mount that they came with. But with a good mount already a newt OTA is no problem and it may even be worth you picking up a good fast second hand newt to experience for yourself what a "fast" ota delivers as opposed to what focal length gives you with what you have got.
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  #24  
Old 22-05-2019, 12:53 PM
Hemi
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So it seems I spoke to soon! The tectonics have moved and the C925 has been shifted (at least temporarily)...(Houston we have a problem thread)!

Pros and cons of the SW 10in F4 vs F5 (price aside)? Purpose would be a multi use scope: EAA and visual.

Not sure of the correct etiquette, and if I should have started a new thread for this....apologies!

Mould free optics and clear skies!

Hemi
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  #25  
Old 22-05-2019, 02:39 PM
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mental4astro (Alexander)
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10" f/4 vs f/5 - coma is the only main difference. It is much more aggressive in an f/4 instrument than f/5.

Best way to relay this is with my own experience with my Newts from f/4 to f/5.

For EEA using a small chip, say 1/3" size, at f/4 there is no coma to be seen. As the chip gets larger, coma will begin to appear, but really for EEA it may or may not be a concern for you. With my 1/3" chip camera, I don't use a coma corrector, and certainly at f/5 even less need to so.

Visual, the only time I use a coma corrector is with my f/4 Newt when using 30mm and 24mm 82į eyepieces. Not vital, but it does clean up the image especially with the 30mm. But remember, I am using eyepieces specifically designed for Newts, in my case these are Explore Scientific EPs, so there is no astigmatism present, only coma. TV eyepieces are also brilliant in Newts. If you use EPs not designed for Newts, any aberrations seen with them in an f/5 Newt will be much more prominent at f/4. Careful eyepiece selection becomes more important with very fast focal ratio Newts.

I hope this helps you.

Alex.
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  #26  
Old 22-05-2019, 06:32 PM
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Ukastronomer (Jeremy)
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Quote:
Originally Posted by Hemi View Post
Thanks Jeremy,
Itís nice that we all are different.
I think a newt will give me a different experience of this hobby, than my current scopes. For me thatís what itís about I suppose. Thatís why I like to observe, image, sketch, use binos, have a go at a few simple ATM/DIY projects etc. (Iím terrible at all of them, I might add!).....Ēresistance is futileĒ, (I think your a Dr Who fan Jeremy?), so a newt is inevitable.

Cheers

H
Actually I am a Babylon 5 fan
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  #27  
Old 22-05-2019, 09:27 PM
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doppler (Rick)
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If you are after a multipurpose newt you could get a dob 8" or 10" and then add some tube rings and mount it on your eq6. I use my 10"f5 for imaging and as a visual scope on its dob base.
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  #28  
Old 23-05-2019, 09:07 AM
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I have a 6 inch 8 inch and twelve inch all f5 and think they are wonderful.
I have not used the eight for visual but have used all for photos.
Don't be put off by folk complicating the job of adjustment.
Alex
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  #29  
Old 23-05-2019, 09:29 AM
Startrek (Martin)
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I totally agree with Alex
I have a 6Ē f6 for AP , an 8Ē f5 for AP and a 12Ē f5 for visual ( all great scopes in their own right)
As for imaging Iím totally in awe of what my new 8Ē F5 can do, it too me 6 months to decide to upgrade but Iím glad I took the advice of many experienced IIS members , Alex included
As for the EQ6-R mount itís flawless , so smooth and tracking is superb, my guiding numbers on this mount are way lower than my HEQ5
Good advice doesnít cost anything !
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  #30  
Old 24-05-2019, 07:03 PM
Hemi
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Thanks for the advice again....
Ok im thinking the 10in F5. Similar aperture to the c925, but very different focal length of course. Should be a good balance of AP and visual. The F4 worries me a little as my first newt in terms of coma, picky collimating, and tricky focusing....have not bought a telescope for 3 yrs so very excited 😆

Mould (or mold) free optics!

Hemi
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  #31  
Old 24-05-2019, 07:30 PM
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mental4astro (Alexander)
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Hemi,

It is wrong to say that an f/4 Newt is more "picky" of difficult to collimate. This is a common complaint though from owners of these fast Newts that are mass produced. What these have in common is they are all poorly manufactured, using components that are undersized or of poor material selection or poorly prepared. It is a real shame as the material choices made by the mass production manufacturers is just to save a few cents per scope, but it means that there are now thousands upon thousands of pages on the net dedicated to fixing their cockups,

What is never heard is of collimation problems with all those big dobs or high end Newts that are f/4 and faster! What these all have in common is they have all been designed and built using the appropriate materials.

I have two 8" f/4 Newts, one is a dedicated visual instrument that I made, the other is a solid tube OTA I can couple to a dob mount or pop onto a gem. The solid tube is a GSO scope, but I've modified the secondary mirror holder and made the primary mirror cell myself. No collimation issues with either scope than with any other Newtonian.

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Also, collimation is far more critical for photo than for visual, as our eyes are not just an active part of the optical train, but also very adaptive, which cameras are not.

There is some good news though about the very fast mass produced scopes. There are some simple mods that can be done to fix what really should have been implemented by the manufacturers. If you want to know what these are I'm happy to explain them. These will cost only a few dollars, which if these had been done at the factory would have cost only cents...

Alex.
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  #32  
Old 25-05-2019, 12:39 AM
Hemi
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Hi Alex, I would be very interested in knowing what the mods are. I was thinking the SW 10in black diamond F4.

Hemi
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  #33  
Old 25-05-2019, 10:56 AM
gjr80 (Gary)
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Originally Posted by Hemi View Post
Hi Alex, I would be very interested in knowing what the mods are. I was thinking the SW 10in black diamond F4.

Hemi
Keen to hear about this too.

Gary
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  #34  
Old 25-05-2019, 11:11 AM
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Add me to the list of interested folks as well, Alex.
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  #35  
Old 25-05-2019, 11:22 AM
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Hi All,

Quote:
Originally Posted by mental4astro View Post
The BEST scope is the one that gets used.


... There is soooo much hype, demonizing and scaremongering about collimating Newts that it is astounding. It is only aligning the mirrors, nothing more, nothing less. And ALL the hype exclusively stems from the word ""collimation"

There is nothing demonic about the collimation process. Remember that a Newt is a scope where the optics are not rigidly held in place, but in spring loaded mechanisms, so if subjected to vibrations, say from a car or setting up and taking down, things can move. And any movement is only very small. Ok, so you need to tweak a screw or two 1/16th of a turn, big deal! The optics will not be horribly misaligned. It's done at the start of your session and you know that if you spend the 2 min that it will take AT MOST, the scope will be performing its very best for you!

Don't make "collimation" your excuse for not getting a big aperture if that's what you really want. More significant is do you have the space to store it and a car to transport it if you need to. Those are much more pressing issues to consider.

Alex.
Never a truer word said.

So good in fact, I'll say it again: The telescope that's best for you, is the 'scope you will use most.

There is absolutely no point at all in getting any telescope that's going to sit in a corner, gather dust and make you feel guilty that you aren't using it, but instead prefer another. Everyone's cup of tea is a bit different.

Yes, Newtonians, unless they are permanently mounted do need to be collimated before use. Would knowing that you had to tune a guitar before you can play it put you off buying a guitar? I mean, tuning a guitar is such an incredible hassle, it takes ages and ages and is so, so fiddly.

Like most things in life that are skill-based (as opposed to talent-based) collimating any telescope takes just a bit of learning but really isn't hard at all with the right tools. The more you do it, the quicker you will get at doing it and before long, it takes no more than a minute or few to get right.

One thing I will take issue with Alex here (in a later comment) is about the difficulty of collimating an f/4 as opposed to, say, an f/6. I guess you are technically correct here Alex: It is no harder to collimate faster f/ratios, but the reality is, slower f/ratios are more tolerant of slight mis-collimation than fast ones. At say f/6 a newtonian that is slightly off perfection will be hard to pick from one that's spot on. At f/4, the tolerances between great and yuck become exceedingly small.

As others have said, guilt should never play a role in choosing a telescope. There are good reasons to pick a big-un, there are good reasons to pick a little-un. There are good reasons to pick a Newtonian, there are good reasons to pick a Schmidt-Cassegrainian or a refractor. Where the balance point is, will depend on how you rank (and how much weight is accorded to) the following factors: cost, ease of portability, ease of use, image fidelity, light-gathering and your own life-circumstances..

Best,

L.
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  #36  
Old 06-06-2019, 03:37 PM
Chapstick
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The first scope I used was a 8" dob which I found very uncomfortable to use, not my cup of tea. I've since had SCT's, refractor and mak-newt all on CGEM which for me at least was the key to enjoying these scopes. I think if I went back to a dob it would have to be around 18-20" for it to have a more comfortable EP location for my height.
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  #37  
Old 06-06-2019, 04:19 PM
Wavytone (Nick)
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Hemi, no I’d say you aren’t missing anything by not having a newt...

For many the reason to buy or make one is simple - they are a way to satisfy aperture fever on a low budget.

Personally I made 5 in my early years - the first two while in high school then as struggling student. At that a time a C8 was way over my budget, a 3” Unitron was hot stuff and we all lusted after the 4” Unitrons fully equipped. But a simple well-made f/7 8” newtonian was vastly superior.

Then John Dobson arrived and big cheap light-buckets were all the rage. Either that or you had an SCT, typically 8-10”. This remained the case for 20 years.

Despite the many significant changes in the last 10 years the big newtonians (dobs) remain cheap and effective if what you want is a light bucket. What the changes amount to is gear you could once only dream of now being affordable for amateurs, facilitating many other things.

Last edited by Wavytone; 06-06-2019 at 04:42 PM.
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  #38  
Old 09-06-2019, 12:35 AM
Hemi
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Thanks to everyone who has commented on this thread.

I am surprised (maybe not!) that no one posted saying that they've never had a newt (and why) and apart from Jared, no ones also said that they dislike them....hmmm I really feel justified in buying one to find out for myself

Cheers

Hemi
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  #39  
Old 09-06-2019, 07:42 AM
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Hemi.
My eight inch Newtonian Telescope cost under five hundred dollars and added to that figure was the cost of a coma corrector which was around three fifty I think...with additional tube rings the thing still cost under a thousand dollars...new.
There is little to fault with it.
And I have still not adjusted it.
Even a six inch does a fine job...I used one for years and would still be using it but I wore it out☺.
You could start with a long fl six which will see you there for about three fifty bucks but I bet you will be happy if you go for the eight.
F5 or F4? Mine is F5 and fast enough for me. I have no experience with a F4 but I doubt they are beyond management.
Alex
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  #40  
Old 09-06-2019, 08:30 AM
Wavytone (Nick)
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Oh I know someone who never did - he opted for Unitron refractors, then a C8. And another with a 130mm APO.
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