dweller25

Yes, mirror dimensions The OTA diameter is 210mm approx.

Yes circumference = 610mm approx diameter = 195mm

@mikeDnight TAKAHASHI - Japan's cure for aperture fever! Great signature 🤣🤣🤣🤣🤣

Yes, good advice - I always try to do this

I find around x180 perfect in my 5” Refractor.

This is what happens when you live in Finland and don’t see the Sun for 6 months 🤪

Wookie power will save us

We are all doomed 😱

If you want the best refractor around 6”….. Takahashi TOA150 F/8 but over budget at £12900 APM LZOS 150 F/8 - £9100 CFF 160 F/8 - 10154 euros TEC 160 F/7 FL - $12500 US

It’s often said that open fronted scopes cool down “quicker” but I have found that it’s not much quicker 🙁 The big advantage of the open tube which I forget to mention is NO DEW 😀😀😀 In reality the 20mm thick mirror holds onto it’s temperature deep in the tube very well so some type of active cooling is essential. Blowing air into the primary helps to remove the boundary layer of warm air that stays on the mirror surface, also there is a good 20mm air gap behind the primary to aid air flow and cooling. No problems with dust on the primary so far but the back is easy to take off for mirror cleaning as per the Tak instruction manual. If i were brave I would drill two holes in the back of the OTA and install two small fans blowing onto the back of the mirror, but I am not that brave 🤷🏻

Hello @refractor2345 I don’t think your first language is English so maybe something is getting lost in translation….. You started by asking about small 60 to 80mm refractors and then start talking about 6 to 8 inch scopes which are very large refractors, or are you talking about reflectors which is the normal type of scope in this size range. You need to clarify. Either way you appear to have a good budget, so you will have a good choice when stock levels improve.

Hello Malcolm, I have the 4” Tak FC100-DZ and the Mewlon 180c and have compared them on DSO’s, planets and the Moon. I can tell you that the views through the 180c beat the 4” refractor in all areas ie resolution, planetary detail and brightness. I suspect it will be very close to the performance of a TSA120. Contrast is the same in both scopes - very, very good. I am very surprised by just how good the views in the Mewlon are - and I am a refractor guy 😱 Plus it’s easy to mount - mine is on a Vixen GP and it’s very comfortable to use. I have put a RACI finder on mine as I found the straight through finder very uncomfortable to use - but I have a bad back ! There is slight image shift during focusing. Cool down - it needs active cooling - I made one of the these - see below - and rest it on the front of the spider - it takes about 40 minutes to cool the primary. Once cooled it’s just like looking through a refractor with really tight stars. I have tried 3xSCT’s, 6xMaks and a Classical Cassegrain which never gave me the wow factor but this Mewlon is so sharp and contrasty it’s amazing. The two scopes compliment each other well - The 4” is a quick cool down grab and go for very low or high power, the Mewlon is more suited to high power - mine starts at x83 with the eyepieces I have but can go to higher mags than the 4” (seeing permitting) and still have a reasonably bright image. The Moon through the Mewlon is super sharp. Hope that answers your question 🙂

The comparison between the TSA120 and Mewlon 180c will be very interesting……

Gary, We have similar tastes, I have Pentax XW’s, Celestron Plossl’s, Classic and Fujiyama Ortho eyepieces, Vixen mounts, Berlebach tripods, an FC100DZ and a Mewlon 180C. Oh and an FS128 😈 …………..

The Apertura is $850US = $1185AU plus a potentially high delivery charge. The Saxon is $999AU so cheaper. Personally I would buy the Apertura for the better mechanics and extras. Although I do prefer white scopes 🤪

Only you can make that decision 👍

I agree with Peter, I had setting circles on my Vixen mount and they were not accurate enough.

As already said a 10” will show more planetary detail and DSO’s will be brighter but at the cost of a heavier base and OTA. Light pollution - can you drive to a dark site ? Personally I would not buy a scope with no warranty despite the lure of extra freebies - although the text in your link says it does come with a 2 year warranty. The Apertura appears to be a rebadged GSO, the Saxon appears to be a rebadged Skywatcher (Synta). Highpoint Scientific are based in the USA so it may be worth contacting them to see what stock levels and delivery options are available. I would suggest the Apertura may be a good buy as the mechanics are better, it’s more expensive but comes with extras - as long as there is a warranty. The Saxon is the better value for money scope. Between the two makes there will probably not be much difference in the optical quality.

@TheTeenThatLovesAstronomy Great choice, very capable scope and excellent value for money 👍

How about screwing a piece of thick steel to a more blue tube ring, for the front of the scope ? Longer dovetail will look better though

Most Astronomers look after their kit and lets face it - in the UK it does not get much use 😂 Do your due diligence and you should be ok.

I agree with Mike, there is a very noticeable improvement in my FS128 over the FC100DZ as the difference is 28% The 10mm difference between the TSA and the TOA is just 8% and the TOA is very heavy - not sure it’s worth the extra expense for visual ?

Yes, thats the secondary tilt, but first you need to get the secondary central to the focuser…..unless its a camera position issue

Your collimation is close, you have some secondary tilt in the North to South direction in your photo probably because the secondary is not central under the focuser - it’s too high in the North direction. But that could be camera placement ?

@Graviton1 There is excellent, free, sky mapping software called “Stellarium” that you can download to help you find your way around the night sky