markse68

Did you re-focus when you tried the filter Paul? You will need to if you didn't as the thickness of the glass shifts the focus outwards a little. And you need to get Jupiter early in the evening now as it gets too low and mushy later

Mark

That's really good Geof and it would be a fantastic resource annotated as it actually looks like what you see through the ep unlike many others I've seen which I really struggle with! (well it has a lot more detail than what I see but the shapes I mean  )

That is very sad news- his absence had been commented on often and he is missed!  

Condolences to you and your family and his friends @thunderbird02 and thanks for letting us know

Mark

17 minutes ago, vlaiv said:

I think it has more to do with water vapor being heavier then the air. There is gradient of relative humidity and air near the ground is moist the most.

Dew first forms on grass, and that is organic material and will cool slowly, but it is closest to the ground and there is the least wind to stir things up.

If your case is placed on some low table or similar - it is going to dew up sooner than the scope that is higher on the mount.

Maybe but there's not a lot of height difference. Interestingly according to this table it seems that emissivity might be linked inversely to thermal conductivity- compare aluminium and copper to glass and plastics and black body

https://www.engineeringtoolbox.com/emissivity-coefficients-d_447.html

Mark

One interesting thing I noticed (to me anyway) is that the dew forms faster and more heavily on my eyepiece case which is plastic than it does on my OTA which is painted aluminium and feels much colder to the touch. I guess the plastic being a good thermal insulator can have a colder temperature at its very surface than the metal tube that conducts heat better but has higher thermal mass so takes longer to cool ?

Mark

I guess it’d need an oversized secondary to avoid vignetting with eps with field stops a long way up the barrel? Not an advantage though 

Mark

2 hours ago, edarter said:

Can someone confirm if this silicone sealant is suitable for mounting the primary mirror in the 130PDS? It says its 'neutral' but in what way I'm not sure...

from what I can find the Neutral cure silicones release alcohol as they cure whereas the other ones give off acetic acid and pong a bit. Not sure if having acetic acid fumes in vicinity of mirror coatings is a good idea so probably the neutral type would be better? Aluminium is supposed to be pretty resistant to acetic acid protected by its oxide layer but not sure I'd trust it. Having said that from a quick search the CN lot are recommending the acetoxy silicones as apparently they stick better without special surface treatments and Dow Corning 732 is recommended. I guess if you let it cure fully with good ventilation the acteic acid fumes shouldn't be a problem

https://www.ebay.co.uk/itm/304502430639

makes me feel a bit better about the state of my mirror coatings 

Mark

Visual is awesome and it’s great you enjoyed your first session and your daughter too. There’s so much to see up there even from light polluted skies. I can spend an evening just trying to find and split challenging double stars. A fun game is trying to identify Jupiters moons visually. Ganymede is the biggest brightest, Callisto is noticeably darker than the others, gets a bit tricky with the other 2 as they’re similar but Europa is the smallest. 

Another nice colourful double similar to Almach is the “winter Albireo” HJ3945

How about some nice triples? Tegmine, Iota Cassiopeiae and Beta Mon are all favourites and in pretty good positions at the moment

Mark

14 minutes ago, RazvansAstrophotography said:

I cant replace the screw because i cant access it because of the broken allen key bit

the screw was loose though wasn't it? Should be able to get it out with a small flat screw driver or something pokey if it was loose

Mark

if the broken bit is jammed in the screw you might be better off just replacing the screw

Mark

Just to add, don't expect too much from Mars- it's getting smaller by the day and is very seeing dependent and with a smaller reflector even at high magnification you likely won't be able to make out much. If you catch Jupiter early in the evening though you should get some nice views and it's pretty dynamic

Mark

Yes your globes are lovely things Mike- how did you make them? 

Interesting you have seen the canals too- maybe it’s a refractor thing

Will have to try to find a copy of that book- it’s all very interesting

Mark

Don’t think it’s Baader though- 1925? a proper antique!

https://www.design-is-fine.org/post/66894393330/dr-westphals-flaschenhimmel-bottle-sky-1925/amp

https://www.experimentierkasten-board.de/viewtopic.php?t=736&p=4981

https://www.experimentierkasten-board.de/viewtopic.php?f=4&t=888

”This kit combines several individual apparatuses, such as universal apparatus, planetarium, tellurium, lunarium, armillary sphere, has theodolite or equatoreal, with crosshair telescope. The bottled sky with a LIQUID horizon without a screw or joint as a navigation device, as a sundial, as a rotatable star chart, enables Foucault's pendulum experiment, eclipses of Jupiter's moons, changes in shape of Saturn's rings and in particular facilitates understanding of the difficult precession, etc. 
The instruction booklet with 125 illustrations works as a course the developmental path of astronomical knowledge. The student comes to the truth through his own research into false paths, which becomes a personal experience for him. 
He acquires his worldview in order to possess it. ”

One sold on ebay for €2k

Mark

Nice! Always wondered why they were called that haha!

Mark

3 hours ago, Space Oddities said:

A new spider came in by the post this morning! It's a very nicely made aluminium spider, with a black matte coating, for my Sky-Watcher 130P-DS. It is said to improve shape of the spikes (no more misalignment leading to double spikes), and helps the scope hold its collimation. It isn't cheap, I believe it's made in Germany (here is the manufacturer if anyone's interested: https://www.backyard-universe.de), but since this scope cost me almost nothing, I thought why not!

 

That looks really nice- I was contemplating the one from Artesky in Italy- looks v similar but maybe not the same

It is fascinating isn’t it! Wiki has a page on it.

https://en.m.wikipedia.org/wiki/Martian_canals

This is an interesting  contemporary report from Leo Brenner who went to visit Lowell and compared what they saw- perhaps Lowell had a sight defect that caused him to see double details which could be interpreted as channels rather than edges? :

https://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1896JBAA....6..266B&db_key=AST&page_ind=2&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES

But i guess auto suggestion (like seeing faces in clouds) combined with strong competition between observers, canal building here on earth all contributed to the mass hallucinations

Mark

I had a cheap ebay phone holder but new phone is heavier than old one and i didn’t trust it to not fall off the ep so been looking for another- this looks the business! Very nice to have all the easy adjustments but it’s very bulky!

And if you ever wondered why these Night Sky Observers guides are so expensive, they are enormous! 

Mark

first pic looks like you’ve been using it as an ash tray Stu! Or maybe for serving peanuts. Wow that was dirty. I’m a bit worried about the primary of my 150p - at first glance it looks pretty reflecty but shine a light and it is dusted with tiny spots. Cleaning doesn’t help so i think it must be oxidising through the coating. It is 30+ years old though

Mark

decent quality cheap chinese finder clamps for a new dual mount i want to make

and a new temp/humidity meter for the observatory- have had to install a dehumidifier as it’s getting way too damp for storing scopes this winter

Mark

Christmas pressie actually- one of the lower cost blowers from Amazon and it’s actually quite nice quality- hoping it will negate the need for dew bands on occasions like last night when my secondary fogged up- quick blast with this should hopefully clear it. And eps

Mark

20 minutes ago, Louis D said:

At f/8 and above, a spherical primary could be considered acceptable for non-planetary observing. 

non- planetary? @Siegfried1969 seems to be getting quite remarkable planetary detail with his 11cm f7.3 spherical Tal 1! I have one too and a 6” Tal 2 version- need to give them another go before Mars gets too far away again. but f4 doesn’t sound a good idea

Mark

4 hours ago, CCD Imager said:

I applaud you for attempting a difficult object from London! Maybe time to transfer your skills to the country side? An hour or two's drive maybe?

Adrian

Yes definitely one for darker skies i think! But i am glad I can see at least something  I don’t think it’s worth spending more time on it from this location.

I had a go at this target in 2021 using a 1m remote telescope in Chile- this is just 15mins data in each RGB- beautiful filter reflections 🤣

Mark

43 minutes ago, IB20 said:

Must say Mars is looking extremely good tonight one of the best times I’ve ever observed it. Managing 300x with the 4mm TOE in the 200P with fantastic albedo detail and colouration.

I was getting good detail and colour contrast at 300x with my barlowed 5mm in the 150p tonight too- it was really good tonight. I wonder if it helps that it is past opposition (looking decidedly not round anymore) and less bright? Seeing was good too of course

Mark

dew stopped play- had a short break after some stunning views of Jupiter earlier and left scope out to cool. Went back out and had a go at Sirius- no joy. Checked Rigel and noticed star diffraction pattern was very noisy but easily saw the secondary. Onto Alnitak- very dim and no split. It was a very clear split last time I was out 🤔 Turns out the secondary was completely fogged  so I have had to bring the scope inside and I'm waiting for it to dry out before more Mars fun.

uodate: scope is clear again   but clouds rolled in  but there’s a big gap coming  

Mark