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I would have thought with the size of the Skywatcher company and there mount range it would make sense to produce there own EQMOD equivalent driver, but more up to date, along the lines of GSS, but get the point about technical support, but a user based forum could take care of most of that…

@Mr Spock Oohh my goodness yes!! I always wondered what exactly those capped holes in my newts' front plastic covers were for! Thank You for educating me Mr Spock! ☺️👍

Yes, I totally agree here. Thanks for the reply…..👍🏻

Intersting question. SkyWatcher produce a weekly webcast, more here. https://youtube.com/@SkyWatcherUSA?si=IMaR3Aa4yywmToFH Maybe worth posing the question to them though I don't expect a necessaily straight answer. 🤐 Cheers, Steve

@F15Rules Awww that's a lovely post! And very wise! 🙂👏

Here's how it works: With a 300mm scope you should be able to get around 125mm without obstruction. So around f12 and completely CA free.

I would think so. What is the edge of the field like with the 25mm Starguider at F10? Do you see astigmatism or is it sharp? I know the eyepiece performs well by the time you get to F12. Yes, but at F10 eyepiece aberrations will be small so the biggest upgrade will be in terms of coatings/transmission/reflection control. If you add a faster telescope at a later stage the differences will be more apparent.

Sorry, you did say you were considering the 140mm and my response was for the 120mm !

That is wholly correct. the red shift of the object has different origins, metrical expansion of space being one, gravitational red shift being another and doppler a third. On a really physics pedandarty note - my understanding is that all objects are "born" into this universe in a state of motion - therefore no need for any initial acceleration to happen to get things up to speed as such. And again, if the object were to be accelerating then this would be shown as a distinctive signature in the successive redshift measurements. So yes we would see the redshift signature and we would be able to discern if the object is accelerating when we take another measurement. I go back to the OP's original question though where he/she asks which direction are the stars moving relative to the Earth. My understanding is that if we only known the red shift taken along a particular line of sight then we only know the direction of movement along that line of sight. We can say the object is moving away from us along that axis. But the star has another component of motion, as you have said, its proper motion. The proper motion is derived from the stars tangential velocity. So to have a more complete understanding of the stars direction we need to measure the tangential velocity as well - it's a vector resolution problem. To be honest I think we are all pushing against an open door here It would be good to hear back from the OP with their thoughts! Jim

In 2017 I was in the happy position, at the age of 61, to acquire my dream scope, an immaculate 1999 Takahashi FS128 Fluorite Apo complete with Takahashi equatorial mount, tripod and a few Tak accessories. It was to be my "lifetime scope", and my wife fully supported the purchase. I owned the setup for 7 years but in the last 2-3 years began to have to accept that my deteriorating eyesight would prevent me from getting the best from the FS128 going forward. Also, the FS128 is a large, bulky scope for it's aperture (although not too heavy), and with our poor climate for astro I.l.reluctantly decided to slightly downsize the scope but to keep the Tak mount. Here is where i think the point I want to make kicks in. When I sold the Tak in February, it was a 24 year old scope, albeit in superb condition. I had 3 firm offers to buy it at the asking price within 3 hours of offering it for sale: I managed to get back very close to what I paid for it in 2017, and with the proceeds I was able to buy a mint 1 year old Vixen SD115S apo (itself a superb scope), and a set of 6 high quality Vixen LVW eyepieces, with some change left over. So the Tak depreciated very little, and I doubt that any reflector would hold it's value in the same way (although the reflector would of course cost far less to begin with). I actually feel that your stated plan to end up with ED 80mm and120mm to 128mm refractors and an 8" reflector would give you an ideal spread of scopes that would cover all your needs for the rest of your observing life. On different objects and in different conditions, a 5" refractor and a 8" reflector can show a fantastic, wide range of objects really well, and are different enough to justify owning both if you are able to. I hope your future work and eye health circumstances allow you to achieve this. All I would say finally, is if/when the opportunity arises, seize it!..your eyesight will likely never be better than it is now, nor your physical strength for lugging equipment around. I have never regretted buying the Tak, and am fortunate to have found a worthy, if slightly less powerful replacement. Good luck with achieving your astro goals. Dave

As above, these are so new that I don't know of any reviews so we need someone to be a guinea pig and find out. Having said that we can look at the specifications and make some guesses based on that. The 15.5/19/25 look like a scaled design so their performance is likely to be similar to each other. I would guess that the 5 elements/3 groups are all in the body of the eyepiece but given the high eye relief/focal length ratio perhaps the first element is a negative lens. The eye relief of the 25mm doesn't quite match for a scaled design though. Elsewhere it is listed as 4/3 so perhaps it is an even more basic design than the other two. Given these are billed as "Flat field" when the same manufacturer also has an "Ultra Flat Field" we can assume that there is a bit of field curvature in the eyepiece, but as these are made by UO I think it is likely that this curvature matches (and so minimises) the direction of curvature in a refractor. Field curvature and astigmatism are opposite sides of the same coin and the design appears too basic to correct both so I think we can assume that that astigmatism will be present at the edges. The 10.5mm is an outlier in that it appears to just be the 10mm UFF rebranded to fill a gap in this line. This is a known good eyepiece and reviews can be found elsewhere. Whether the lower cost has been made possible by some cost cutting somewhere (coatings?) or the manufacturer are simply accepting lower margins remains to be seen. The 3.5/5.5/7.5 look like a "modern" design with a standard set of lenses in the body and a negative group in the nose. Specifically it looks like these are based on the 15.5mm. See how the outer body design of the 15.5 and 7.5 is identical in size. As the number of elements and groups increase by 1 this is a simple negative lens so the 7.5mm is probably quite nicely corrected but maybe the 3.5mm is pushing the design a little bit too far so it might be a bit soft in comparison. Also note how the AFoV has been trimmed from 65° to 60°. Perhaps this is a marketing trick to make the 10.5mm eyepiece not stand out so much, but also consider that if we double the magnification moving from the 15.5 to the 7.5 then we also double the size of the aberrations at the edge, which is indicative that perhaps the edge performance is not so good and needed to be hidden. If your only desire is for use in an F9 scope the 25mm might perform well enough, but if you also wish to use it in the F6 scope I would suggest spending the additional money on the 24mm UFF instead (or ES68, Panoptic).

At this price I may very well include it with my next purchase… A few of these might make a nice outreach set.

@Flame Nebula Just a heads up, I don't know how quickly or not you seen my reply but i've just written a bit more to it, bits I forgot to mention!

I think Askar hide their sins in the large spot sizes, judging from the comments in that thread?

@Flame Nebula Assuming your question relates to the 5inch refractor vs 8inch newtonian? Oh yes definitely. Impo the views of planets like Jup. and Sat. and others is much better through my 8inch newt than my "almost" 5 inch refractor. One thing to note, your local seeing conditions can have a big effect your views, so when it's really bad seeing, I have found the views to be slightly better through the refractor/120mm. I believe the reason is when seeing is bad, the ability to resolve fine details in planets is limited, and larger aperture 'scopes simply help you "see" more of the bad seeing, if that makes sense? ( I don't know if you know already, but just incase, seeing refers to the atmospheres "steadiness". When its bad, the views of planets, particularly at higher mags, are not very pleasing. A good analogy is looking at pebbles in a stream, where they appear all wobbly n blurred ) My personal advice would be get an 8inch newtonian, they're relatively cheap, the ratio of pounds spent per mm of aperture is as good as you'll get in astronomy! They pack a heck of a punch for the money! Other members may have different opinions but this is my own personal experience! Hope this helps!

The USB ports on modern mounts permits direct access to update firmware via a downloadable application from their main website. The fact that it also provides an option to control the mount from a PC via a 3rd party application is a bonus for those wishing to go down that route, but its not something Synta actively promote. The only difference is the wi-fi dongle, which has an android app, and the start adventure, which has PC and phone applications to control the mount. It's probably down to the cost of setting up the infrastructure to provide technical support. You only need to look through forums and user groups and see the posts related to PC connection, guiding, etc which if Skywatcher had a support line would be directed towards them. But I agree with you, it does make sense to provide an application along the lines of EQMOD or GSS, even if it was stripped down and had less options.

Correct it is, although not exclusively as has been commented on. As such, any red shift measurement taken along the line of sight on an accelerating object will reflect that changing velocity (hence change in red shift). It is a well practiced technique - here on Earth it comes in handy in my car to stop me bumping into the car in front when I have cruise control on Jim

If one don't wear eyeglasses when observing , the eye relief of the 25mm and 19mm eyepieces is too big. You fail to find and hold your head/ eye in the right position, resulting in a lot of fleeting kidney bean aberration. This is what is happening to me with the 32mm Plossl I need to modify in order to be useful. For me, and others like me, an eye relief of 15-16mm is plenty enough. But it is obvious that producers and dealers have forget about us and leaving us no other option than not to buy. So be it. All I need is to get the two SV Bony zooms due to arrive next week. And a 4mm Radian. No more eyepieces needed here. Mircea

I realize that the Doppler redshift is a product of velocity, not acceleration, but my point is that, to have a velocity, an object must at some point have been accelerated. The cosmological redshift, however, is not introduced by velocity but by the expansion of the space through which the light is travelling. While following the same formulae, these redshifts are not of the same origin. Olly

Yes, but still the Doppler Effect is a function of velocity. You will see progressive change in velocity but you have to do at least two mesurments of Doppler Effect. For each of them you will get diffrent velocities.

Thanks Wes, I'll probably see what jupiter looks like without, and then consider it. I was more interested in if it would allow extra details to be seen. Did you not see anything extra at 8" aperture?

I discovered this when painting a steel handrail in front of the house. On a hot day it flowed out nicely. Olly

If the object was accelerating through then as we take and then retake the red shift measurement we would see it progressively change reflecting the change in velocity. Jim

@Flame Nebula Hi again. I've used a variable polariser many many times of 7-8 years doing visual and in my experience they aren't much use for Sat. and Jup. in terms of reducing brightness because brightness of those planets has never been an issue for me. One planet that I would argue the VP is essential for viewing though, is Venus! It is stupendously bright! You definitely need a VP to view Venus, and you get to resolve it's phase! It's very pretty! I must also qualify the statement, by saying I've only ever used the VP with an aperture of up to 8 inches, so it's entirely possible larger aperture 'scopes might benefit from it when viewing Jup. and Sat? I'm other much more experienced members can advise you on that!

It doesn't matter whether the mass is accelerating or not. The Doppler Effect is a function of velocity, not acceleration. When you measure a spectral shift, you do it at a specific point in time at which the mass has a specific velocity - even if it is accelerating.