Deadlake

Yes great scope, looks very compact. Looking at one as well, maybe 210. Only reserve is cool down and effect of seeing on usage.

If AP wouldn’t you want a faster scope, say less then F6 and with a larger imaging size to illuminate the sensor?

The aperture may not increase however obviously time of capture would decrease, which seems a step up.

Above 130 mm usually into mirror based Astrographs.

11 hours ago, mikeDnight said:

 With the cold damp, or moist warm air trapped within an observatory, there's the potential to promote fungal growth on the optics.  I kept a pair of 15X70 binoculars permanently in my observatory, and despite them being permenantly capped when not in use, after only one year both objectives had fungal spots. Even eyepieces can fall victim if they are left in an observatory, or boxed away while condensation is on the lenses. A friend once loaned me a pair of 18mm Tak LE's that he'd kept in his observatory. Both had fungal threads between the elements.

What about a case and some silica gel or similar to keep the scope dry? Walking the scope in is an opportunity to drop it, wet grass etc.

8 hours ago, jetstream said:

Lockwood advocate a 300mm mirror as a reasonable size for a RTF. Using this and with sec to focal plane distance of 190mm a 73mm secondary gives a great 24% central obstruction.

Or maybe one of these https://www.loptics.com/articles/okietex2009/okietex2009.html

One thing to note: being able to use Ethos class eyepiece at the "right" exit pupil really ups the views with a RFT...

M24, got to say again- this is a must see and study...

What about diagonal and EP.

3” explorer scientific and 30 mm EP versus greater then 44 mm aperture 2” and 41 m panopticon or 40mm paragon. How would image size the scope could illuminate effect this?

9 hours ago, vlaiv said:

Well - you can take 6" F/4 Newtonian + coma corrector and you'll get the same thing - well almost. Not sure how well corrected the field will be - but for low power visual - probably good enough.

6" with lower mirror reflectivity and central obstruction will provide you about same light gathering as 5" refractor.

Then, there is real deal, but with a bit of false color

https://www.teleskop-express.de/shop/product_info.php/info/p7788_Bresser-4827635---127-mm-Refractor--f-635-mm--OTA.html

It is 4 lens elements design - although that is probably just to lessen chromatic aberration it could also be that field is fairly flat?

A newt would work, question around size of central obstruction. Boren-Simon powernewts are rated for this, as would the usual suspects found here:

https://www.teleskop-express.de/shop/index.php/cat/c58_Telescopes-with-field-corrector.html

On 11/02/2021 at 14:31, vlaiv said:

127mm F/5 refractor telescope is capable of providing that low magnification with ~42mm eyepiece while giving you something like 4.3° of FOV.

 

we only really needed this line to answer this....
 

Televue 127mm/ F 5.5

LZOS 130mm/ F6

Sharpstar 121 DQ / F5.5

I can think of, none are cheap.

13 minutes ago, Stu said:

Not totally sure of the definition of an Astrograph, but agree that it should have a flat, coma free field. Would a fast dob with a coma corrector be classed as an Astrograph I wonder?

I’d say yes for the DOB. Also large imaging circle as well, as discussed in article.

@FLO Ignoring border issues, are prices of Europe sourced items going to increase, e.g. Baader for instance?

3 hours ago, Highburymark said:

Skywatcher prices have been so competitive for so long - significantly below the rest of the market. Maybe Synta has calculated - in these unprecedented times - that among all its brands, Skywatcher can absorb the biggest price hike? Just a theory, as the increases seem surprisingly high. Will be interesting to see how the rest of the market responds.

The free lunch of lower prices from China could never last. If transport costs did fall, I suspect cost of living rising in China will make up the difference. The new normal.

3 hours ago, John said:

http://www.ianmorison.com/rich-field-telescopes-and-wide-field-observing/

Interesting read John, this part 

t is important that the telescope used gives good star images out to the edge of the field and for a Newtonian a coma corrector such as the Baader MkIII MPCC would be required whilst for a refractor a field flattener such as the Teleskop Service 2-inch TSFLAT2 should be used.  Very few telescopes will give a sharp flat field over that encompassed by the Explore Scientific 30 mm eyepiece and these would be termed astrographs – but few of these have image circles greater than ~44 mm.

Is Prof Morrison suggested to get the richest view, you should consider using a fast scope that’s has a field flatterer and a minimal image circle of 44mm. 

It’s not just a fast telescope that is required, it’s an Astrograph?

2 hours ago, mikeDnight said:

 However, I'd still carry the tube assembly back into the house after every session. I think the worst place to keep a telescope is in an observatory.   

Any reason why, you think humidity will compromise the scope? 

A filter wheel, no more fumbling around with filters in the cold night. Always fun making sure they don't drop out. Also bit more back focus for larger EPs.
 

1 hour ago, mikeDnight said:

Brilliant idea!  I've actually thought about constructing a dome for my observatory rather than the run-off roof I have at present. Although it will still need to be cool, it will offer a little more protection from cold winds, and will aid in maintaining dark adaption. I think this might be a project for this spring! ☺

I’m tempted too, but more around the time taken to setup each night. Just going out and powering it up is more attractive. Out of interest if you have an observatory why limit yourself to a 4”?

5 minutes ago, mikeDnight said:

It's rare these days that I'll stay out long enough in sub zero temperatures for my lens to dew.  Going back to the time i had my NP101,  I remember sitting on a deckchair ankle deep in snow and sweeping the sky for two or three hours. My next door neighbour called to me over the low garden wall "Youre mental you are! I've always known you're simple"!!  (She's a sun worshiper)!   I replied to her with some witty comment, but after she'd gone, I realised that although my body was as warm as toast, the cold night air I was breathing was making me wheeze. That was back around 2007/2008. Since then I've been careful not to let the cold affect me like that anymore. Now I'm more a creature of comfort and relish the milder spring nights. Perhaps I'm just getting soft as I get older.

What about a dome observatory, better than a roll off? How much protection dies a dome give against breathing cold air???  

So how cold does it have to be before you have to consider this, presume function of humidity as well. Number of ponds and streams around where I live as well. Is @mikeDnight red light test is as good as any to see if there is water present? I can feel moisture on the tube when I take my refactor in, so guess that implies there is a enough water around to cause issues if not allowed to evaporate.
 

Hopefully will not have cold nights like this for some time, doesn’t seem to improve the seeing which is not what I expected.

17 minutes ago, mikeDnight said:

According to some on CN, the FC100DZ might not be available in the state's until August. That could mean a TSA 102 in top condition would bring a high price.

Over £100! 

You could step up to a TSA 102 and no one would notice in the immediate vicinity....😃😄😊

You could start a thread somewhere title "Is the TSA102S the best 4" telescope  ever".  Free advertising..... 😀

Hm make a nice replacement for my Vixen, might even get to my house before my LZOS turns up. I'm sure it will be snapped up.

@JeremyS is above his Tak allowance. 😀

2 minutes ago, Kon said:

last night without the moon the sky was bright from the stars and can make out where the milky way is. i can usually see some of the open clusters as a smudge of bright patch without a telescope. the nebulas and galaxies  i have seen so far are bright withe sky being quite dark around them. i leave in the middle of nowhere with the closest town being over 10 miles away and smaller villages 5miles or so..

I get surprised thats classified as Bortle 4. family live near Brecon Beacons and thats Bortle 3, say > 21.5 SQM. 

17 minutes ago, jetstream said:

I gotta go get birdseed- my little cold red birds out there look hungry! puppy needs some treats too, back soon.

What bred of dog have you got?

18 minutes ago, jetstream said:

Can you define Bortle 4 in your own words from your own observations?

The Bortle scale is a little losely defined, so I can see why you don't find it precise. A large range of SQM is covered each scale in the Bortle system.

Hence the interest in NV, I'd like to see Nebulae better, only possible using filters. 

Also I find SQM directional, towards London I don't really look as the sky as effected by light pollution. 

Below is close, but also quite a wide description.

• the zodiacal light is still visible, but does not extend halfway to the zenith at dusk or dawn
• light pollution domes visible in several directions
• clouds are illuminated in the directions of the light sources, dark overhead
• surroundings are clearly visible, even at a distance
• the Milky Way well above the horizon is still impressive, but lacks detail
• M33 is a difficult averted vision object, only visible when high in the sky
• limiting magnitude with 12.5" reflector is 15.5

M33 needs a scope where I live.....

2 minutes ago, jetstream said:

I truly dislike the Bortle scale and no offence to him. I hear "I'm Bortle 3" or "ok I'm Bortle 3/4 but sometimes 5".

I now go by the Milky Way (and SQM-L, NELM) - if you can "just see" the MW RFT obs will be diminished. If it looks bright but with limited structure ( a transparency issue) RFT view will be good. If the MW shows bright jagged structure with its spurs showing- run for the RFT! and every other scope you have!

My skies run from 21.4 SQM to 21.9, NELM at least 6.8. Transparency runs from poor to excellent.

I usually only do reports when conditions are excellent

Fair enough, in my garden around 20.5 SQM using Dark Sky Meter. I should measure some more to see how it varies.

2 hours ago, jetstream said:

Please note that filters are not magic... you need dark transparent skies for these objects. I sold my house in town and moved up in the bush for dark skies...

How dark is it where you live, I have just Bortle 4 skies. 

2 hours ago, jetstream said:

I bought the Binotron 27s for a few reasons including a discussion with Russ. I told him my set up and wanted the binos to work with any of my scopes. He immediately knew what to do- he made an extension for the system to focus in my newts, no charge. This system works in my fracs and newts extremely well.

If I was over there I would look at the new Baaders, research them - but they look good to me. Good EP holders are a must.

Ever tried to see a report on these:

https://www.astronomik.com/en/infrarot-passfilter-infrared-pass-filters/proplanet-807-filter.html

meant to help out with planets when poor seeing, however that could start another thread. 😃

1 hour ago, jetstream said:

First off dark skies are a must for rich field viewing, second many scopes can provide it including my 24" f4.1. Many will argue this but whatever. Again getting under dark skies is a must to be able to see what a RFT (or any other) has to offer IMHO.

DaRk Skies, how dark. Less then or equal to Bortle 3?