John
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Posts posted by John
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1 minute ago, vlaiv said:
That is not quite what I had in mind.
Thing that we measure needs to be the same - but tools used or person doing it can change.
If two unrelated people perform same technique measurement on object and get the same result - I have more confidence that none made an error in doing the technique
If two different measurement techniques are performed on an object and we still get the same result - then I have more confidence that measurement reflect object properties.
I understand what you mean. In reality though, how likely is that to actually happen in the world of amateur telescopes ?
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No moon either
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4 minutes ago, vlaiv said:
I think that best test of the "test" is repeatability.
Can the same result be obtained by another test and can two independent testers using that test obtain same results.
If so - then I'd say test is valid.
He did another ED120:
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6 minutes ago, Deadlake said:
They are using the correct make of scope.. 😃
He has tested loads of scopes:
http://r2.astro-foren.com/index.php/de/
The tests of the Synta ED120's are interesting, eg:
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How accurate / useful are the tests that Herr Rohr does considered to be these days ?:
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I keep my Quikfinder off the scope when I'm moving the 12 inch dob around and when it's stored. It clips on and off quite easily and seems to hold the alignment with the main scope quite well.
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5 minutes ago, Raph-in-the-sky said:
To me the main issue is the narrow field at high power. For example, my zoom which is a basic Celestron 8-24mm provides only 40° of AFOV at 8mm.
It's usually the other way around with zooms - wider field at the short focal length and narrower at the longer focal lengths
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I have a 7.2 - 21.5mm zoom. One like this:
https://www.firstlightoptics.com/ovl-eyepieces/hyperflex-72mm-215mm-eyepiece.html
I often use it with a 2.25x barlow lens to get a high power zoom - 9.55mm - 3.2mm.
I also have a range of top quality fixed focal length eyepieces (Pentax and Tele Vue) and the zoom and zoom barlow combination compares surprisingly well to those in terms of optical quality. If I'm being very fussy or have a particularly challenging target I will use a fixed focal length eyepiece but very often the zoom does the job well.
The area that the zoom does not compete with is the field of view at the longer focal length end which is rather narrow but this is also the same with most other zooms.
I used to be a bit cynical about zoom eyepieces but over the past couple of years they have found a steady place in my eyepiece case and have proved very useful.
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7 minutes ago, NorfolkGazer said:
Yeah its a 70-700 refractor. I think that they both have great positives, and don't think that either will look out of place. I'm thinking the Rigel will be around the same height as the basic finderscope that is attached to the Skylux currently. I'll have read on both of them, IIRC the Rigel has pulse built in where the Telrad needs a retro fit kit. Cheers for the advice.
I don't use the pulse feature on my Rigel to be honest with you.
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You might find that the smaller footprint of the Rigel Quikfinder looks more at home on the thin tube of the Skylux EL which I recall is a long 70mm aperture refractor ?
It fits in a similar way to the Telrad - a base that you stick to the scope tube and the finder then clips on and off that. I use one on my 12 inch dobsonian.
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8 minutes ago, Jm1973 said:
I'm focusing on the roof of a building about half a mile away. I thought it was the other way around though? ie. it's further in when focusing to infinity. I am probably wrong.
You are correct - when focusing on closer targets, the focuser needs to move further outwards.
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8 minutes ago, Scooot said:
I thought mine wasn’t working at first either, but then I realised the speed was set too low to notice any movement.
Yes, I've been caught out like that as well !.
At low tracking rates (ie: 1x, 2x etc) the motion is not really obviously visible.
Try one of the faster tracking rates (I believe the mount slew at up to 800x) and you should see it moving.
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There are some hardy folks on here and I admire the perseverance
Not me though. If I get too cold I stop enjoying it. Fortunately my usual observing site is about 1 metre from a nice cozy warm room so I can pop out, do a bit of observing then pop back inside to warm up, have a warm drink and consult the star charts for the next target.
Probably an unusual arrangement but it suits me just fine
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I think the secondary mirror does have collimation adjustment with these. It is the primary that is fixed.
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44 minutes ago, jock1958 said:
As well as that focuser upgrade @FLO have added lots more More Blue goodies!
Yep - these 95mm tube rings look tasty
https://www.firstlightoptics.com/tube-rings/more-blue-95mm-tube-mounting-rings.html
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19 minutes ago, Jiggy 67 said:
This is what you need
Though I would leave them be unless you really need to clean them
That's the kit that I have used for the past few years. It works very well.
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Great report Gerry !
I've noted that "finger" a few times this year when observing M42 with my 12 inch dob. Those "scallops" out of the adjacent arc of nebulosity are distinctive as well, when the sky is nice and transparent.
So much to explore in this nebula - whole sessions can be spent there !
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If you are looking for DSO's keep any light as dim as you can. My personal preference is no light at the scope when I'm going for the really faint stuff.
For planetary and lunar observing it does not matter. In fact dark adapted eyes are less effective in picking up subtle planetary features.
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Just a further thought.
Both the 100mm and 76mm Taks are superb scopes in their aperture of course.
It's easy for us to urge you in the direction of the 100mm for lots of good reasons but at the end of the day it's your money and the way you want to approach the hobby that matters most and I would not feel easy if we pushed you into a decision that you were not ultimately comfortable with.
If the smaller, lighter, easier to mount scope will get used more, that's the one to go for
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1 hour ago, Surfer Chris said:
Thankyou again for your responses over the weekend.
Going to see what eyepieces I can find in stock today.
Deadlake - just re-reading your comments above regarding maybe requiring a different mount for the 100DC at high powers. I guess this was part of the difficulty I was having between the choice of 76DCU & 100DC originally. I wondered if, in reality I would not be able to take advantage of the 'really high powers' that the 100DC can potentially offer on the lightweight Scopetech mount (I have heard 200x plus is fairly common). And therefore it may have been better to stick to the smaller 76DCU where I might be able to utilise the full possibilities of the scope in my desired mounting arrangement.
Presumably, even if the mount doesn't work well with the super high powers, I guess generally I will see a significant improvement going with the 100DC over the 76DCU for the 'average' powers? I am guessing if I went with the 76DCU I would typically be observing in the range of up to 150x max, and with the 100DC maybe up to 200x max? And for a given magnification (e.g. 100x), I am hoping the 100DC will give a crisper and brighter image with more resolution. So FC100-DC still a better choice even for the lower 'typical' magnifications. I hope that my understanding is correct!!!
On another matter, I was thinking of mounting a Tak Clamp directly onto the Scopetech Zero Mount (apparently you can do this). So I wouldn't have a dovetail bar and keep the weight down a little more. This would mean that I would be using the Takahashi Clamp to de-mount the scope and for adjusting balance etc. Do you think this is a bad idea? Would I be better to get a dovetail bar for balance adjustment? In this case I would then probably get and ADM clamp rather than using a single screw to hold the scope...I don't like the idea of a single screw point holding up such an expensive item.
I use a Vixen type dovetail bar bolted (2 bolts) onto the tube clamp to hold my FC100-DL. It is not heavy and it does make adjusting the position of the tube easy, should you need to do it. Some people use tube rings and a dovetail bar but the tube diameter of the FC100's is 95mm which is quite hard to find rings for. IMHO the clamp plus DT bar does a good job anyway.
100mm is, IMHO, preferable over 76mm even at lower magnifications. More resolution and light grasp is beneficial even at lower powers.
BUT ...... portability is not such an issue for me and my mounts are heavier duty than the Scopetech I think.
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Great report Louise
It's been a while since I've seen a clear sky here so it's nice to read that they still come along !
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My first proper scope had a similar design. It was a 6 inch F/6 newtonian made by Astro Systems of Bedfordshire, UK back in the 1980's. The secondary was adjustable but the primary was fixed. These scopes were all metal though and carefully machined to maintain what was termed "refractor-like optical alignment" in the brochure. It worked rather well as I recall
So if the scope is manufactured and assembled with some accuracy and care, it is a viable approach. This was my Astro Systems scope:
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4 minutes ago, wulfrun said:
You'll have to excuse the pedant in me...if you can see it, it would be there all night I'd hope (weather-permitting) 🙂
(I couldn't resist, abolutely no offence meant)
No offense taken at all ! 🤣
It was a daft comment for me to make
It must be the couple of glasses of wine I had with supper talking !
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3 minutes ago, ecuador said:
Don't worry, PS Align Pro is the version for Amateurs.
I added the Daytime align tool Jiggy mentioned when I was going to the 2017 eclipse, but it seems that many of my users use it for night-time alignment when they lack a view of Polaris. So, the version currently under development has a new "Hop Align" tool, that allows you to center any star you can actually see (preferably not too far from the north), before the app "hops" you to the Celestial Pole, having used the reference star as a calibration point. Anyone interested in trying it out early, just pm me with an email to add you to the beta test list. Otherewise it should be in the public version soon enough
Thanks. Is it available for Android as well as Apple ?
I'm lucky - I can see Polaris all night from my back yard and have no problem finding it using the "pointer" stars in Ursa Major. My mounts are un-driven alt-azimuth so I don't need to align them.
MTF of a telescope
in Discussions - Scopes / Whole setups
Posted
I didn't try translating it. I just looked at the pretty pictures
Unit to unit variability is an often discussed issue and, in the past, has been used to make the case for buying a premium brand at a premium price.
I suspect that production consistency is pretty good from all the manufacturers these days though.