Gfamily

This was brought home to me when visiting Mount Palomar (as a tourist) several years ago. There's a small gallery of exhibits that has a view into the dome - and some small vents, through which you could feel a flow of very cool air seeping out of the dome.  Their weather forecast predicts the air temperature expected for that evening, and the dome and scope is pre-cooled to match so as to reduce the thermals when the dome is opened. 

Just for clarification, insulating scopes is done to reduce thermal currents and improve the quality of the image. It's an alternative to having a longer 'cool down' time, which can be significant for Maksutov scopes. 

Insulating may have a minor effect on dewing, but only because it'll keep the corrector plate slightly warmer for longer, but the benefit will be minimal. A dew band will be far more effective. 

1 hour ago, Marvin Jenkins said:

Hi Gfamily, the reason I said that is because I can find so little scientific enquiry with regards to Arp’s claims about questionable red shift (except his own). I have spent a great deal of time looking for published papers examining his claims.

I find untold quotes, and comments with regards to ARP being wrong in websites to do with this subject. I am struck by how resistant many sources are to anything that questions Big Bang theory. It is not like saying the mans name three times will make him appear!

Furthermore, no matter how much we do this, I always end up on the end of a reply saying “ARP was wrong, red shift proves it” which is like saying you are right because you are right. You maybe right, but at the end of the day Big Bang is still a theory, not a fact.
 

Marv

Arp's principal claim is that alignments between galaxies and AGNs are far higher than statistically likely, hence there is a physical cause for the correlation, and hence that red shift (for certain classes of astronomical objects) is not correlated to distance.

At the time of his claims, we didn't have the data about the distribution of quasars that we have now. The main argument against isn't "red shift proves Arp wrong", it's "More data shows that Arp's principal claim isn't correct". 

Picking individual cases and saying "this looks like it's closer than that", or "these two things look like they are connected" is a weak basis for challenging the generally accepted cosmological model. 

Extraordinary claims require extraordinary evidence, and if the principal item of evidence (the statistics) has been discounted, then reverting to individual 'odd looking' cases is not really strong enough.

On 10/10/2020 at 20:14, philthy said:

I just think Arp's ideas have been binned,  without due examination

On 10/10/2020 at 20:44, Marvin Jenkins said:

I am not an advocate of one theory or another, but I do get annoyed when data, no matter how annoying is ignored. I get more than that, when it is discredited and sidelined for little scientific reason

Ummm, what makes you think there hasn't been examination of the ideas, or that they've been dismissed for little scientific reason? 

It's always worth spending some time learning the names of "landmark" stars:

• Merak and Dubhe, the two pointers in the Plough,
• Polaris - of course - not particularly bright, but the brightest in its area of the sky
• Mizar (second star from the end of the handle of the Plough)
• Arcturus - follow the curve of the handle and you'll reach Arcturus,
• In the Summer, the three stars of the summer Triangle: Deneb, Vega and Altair (lower down)
• In the Winter, the main stars of Orion (Betelgeuse and Rigel),
• The Winter hexagon - Arcturus, Capella, Castor, Procyon, Sirius and Rigel.

If you can identify these as they appear in their different times and locations across the year, you will be well on your way to finding alignment without any stress,

Aplogies to those hearing me say this for the umpteenth time, but a great help for finding the suggested stars is to get yourself a 12" Philips Planisphere - it shows the whole visible sky for your time and location in a single view, and has the brighter stars named. Yes, you can get something like this on an app, but I don't think there's anything as effective at showing how the night sky changes hour by hour and month by month, with constellations being visible firstly in the east, then moving west as the hours go by and as the months go by.

Related to NGC7319 https://chandra.harvard.edu/blog/node/150

I have driven it from Stellarium mobile plus (on Android) - which was only £7.49 .  Once aligned (using the Synscan app) it was spot on when performing GOTO from Stellarium plus.

You can always request a refund if you try SkySafari and don't like it. 

16 hours ago, adyj1 said:

And - as I understand it under the Consumer Contracts Regulations - the retailer does not have to pay for the return postage if their terms and conditions state this. (if it isn't stated, then the retailer must pay the postage).

The retailer can also deduct an amount from the refund commensurate with the loss in value of the product. So if a retailer can only sell a returned item it if they discount it, then they can deduct this amount from the amount refunded. 

You have no legal right to buy something online, open it and then expect to return without any cost to you, unless it is faulty or not as described. Even though Amazon let you do it 😁.  

A slight amendment - 

The retailer can only deduct an amount (for loss of value) in respect of anything 'beyond what is necessary to establish the nature, characteristics and functioning of the goods if, in particular, it goes beyond the sort of handling that might reasonably be allowed in a shop'.

So opening the box, checking the contents and deciding you have changed your mind should not affect the amount refunded. 

https://www.legislation.gov.uk/uksi/2013/3134/regulation/34/made

Yes, the Celestron NeXYZ is a step up from the cheapest phone adapters.

It has a simple and easy to position clamp to attach to the lens, and rack and pinion gears to control the positioning.

In addition, it has a third axis of movement, so you can find the optimum distance from the eye lens. 

The light pollution map shows some promising dark sites. 

https://www.lightpollutionmap.info/#zoom=8.82&lat=51.1502&lon=0.7531&layers=B0TFFFFFFFFFFFFFF

2 hours ago, almcl said:

Here's a website that predicts seeing.

https://www.meteoblue.com/en/weather/outdoorsports/seeing/38.043N-77.350E

It looks as though you have a strong jet stream over Virginia at the moment and that often results in poor seeing.  Ironically good transparency (clear skies) is often combined with poor stability (roiling air) whilst poor transparency may be accompanied by more stable air.

Frustrating isn't it?  When you get a rare night that is both stable and transparent, make the most of it, in UK at least, they can be quite rare!

That's a nice site 

An alternative way of checking the Jetstream is to use this 'global view' 

https://www.netweather.tv/charts-and-data/global-jetstream#2020/10/01/1200Z/jetstream/surface/level/overlay=jetstream/orthographic=-68.58,37.96,712

I think they can calculate the thermal gradient from space and work out the likely temperature at the relevant depth, which is below freezing point of pure water.

Hmmm, that sounds unfortunate. What is your power supply?

The usual suspects would be to check:

Is the cable properly clicked into place?

Is there any damage evident to the cable?

How's the power? Low batteries can cause odd effects? 

My principle thought is that the SA was designed as an imaging platform, whereas the AZ GTi wasn't, so if the latter doesn't work as well as you expect, you're really not in a position to return it. 

I can't give advice, but I've recently borrowed an Altair 72ED and mounted it on a SkyWatcher AZ GTi and under dark skies it's the most fun I've had for a long time with a telescope. 

Once aligned, the GOTO has been spot-on, and using the app on my (android) phone has not caused any grief (the only thing, I guess is that you need to make sure you charge your phone early in the evening rather than overnight). 

It does need dark skies though. 

3 hours ago, Marvin Jenkins said:

I’m back with an answer. Fried my brain to tell the truth. One of the hardest parts is to find accurate data to start with.

Q1. 12.8 million

Q2. 310

Q3. About 2000

Q4. 1200 square degrees

Q5. 2000 galaxies covering 372,000 Quasars at an average of 186 quasars per galaxy.

How did I do?

Marv

Oooh, 

Q1 I guess you got from here, but I'm not sure where that 'function' came from, and of course, that's for quasars down to magnitude 23, whereas  MK205 is a thousands (or tens of thousands) of times brighter. 

Q2 The Sloan Digital Sky Survey has identified in the region of 5-600,000 quasars (according to the wiki), so the number may be a bit less

Q3 Hmm, maybe (are you including dwarf galaxies?)

Q4 What!!!?!!! NGC4319 is about 3' by 2.5' - which is about 1/480 of a [square] degree, so even if there were 2000 galaxies, that would only be about 4-5 square degrees in total

Q5 Do we see ~200 Quasars behind galaxies? 

Question - what is the 'expected' magnitude of a Quasar at about 1 Bly distance?  I'm trying to find its magnitude. 

9 hours ago, anthonyyaghi said:

Would it be better to get a like a 4mm or 6mm eye piece or an x2 barlow ?

One advantage of a 2x barlow is that it can be used with any eyepiece, so it's got multiple uses. Get a 30mm eyepiece for wide angle views, and  the barlow means you have the use of a 15mm for free.  

Another is that using the barlow means you (mostly) keep the benefits of the eyepiece - and given that a 10mm eyepiece is likely to have a bigger eye lens and better eye relief than a cheap 5mm, it can make it easier to use. 

3 hours ago, Marvin Jenkins said:

The maths to calculate the number of quasars expected around a galaxy!!! I said I read the book Bang and looked on the web for an hour not completed a degree😂

Seriously though, how does one go about such a task?
 

I may be wrong, but my thoughts would aim to keep it as simple as possible - so would be along the lines of... 

Q1 "How many quasars do we know there are?"

If we assume they are randomly distributed the next Q is

Q2 "How many are there per 'square degree' on the sky?"

Now; we know NGC 4319 is a close-by (relatively) galaxy - so its angular size is larger than most. 

So let's ask  -

Q3  "How many galaxies are as close (or closer ) as NGC4319?"

and Q4 "What's their combined angular size?"

Then you can ask -

Q5 "Given the total angular size from Q4; how many Quasars (as per Q2) would be covered by a part of a galaxy as close as NGC4319?"

I think I read somewhere that Mk205 is at a distance of about 1Billion Ly, so the foreground galaxy probably did exist when the light was emitted. 

2 hours ago, Beardy30 said:

Am I perhaps better getting the Sky-Watcher Skymax 127 (EQ3-2) model 

EQ mounts take more setting up, so if it'll mean you take it out less often, I'd advise against (at least to start with). If that's not a risk then you could. I'm not sure there are big advantages in an EQ mount though. 

4 hours ago, Marvin Jenkins said:

Just a presumption, but if one galaxy NGC4319 can create gravitational lensing then I would expect most galaxies to have a QSO as a neighbour. My basic idea is that if we are looking at a galaxy and it has another some distance behind it, it would be shown by lensing. With the amount of galaxies lensing should be evident a lot of the time I would have thought.

Marvin

Why?  Have you done the maths to calculate how many quasars you would expect to be located within the extent of a nearby galaxy? 

Try it; it's really worth doing it yourself.

Bear in mind that NGC4319 is relatively close for a decent sized galaxy, and they get 1/4 sized smaller for every double the distance. 

39 minutes ago, Marvin Jenkins said:

I had to laugh though. Put in a search for NGC4319 in the NASA Hubble site and it came back with unknown.

I tried again in upper case and the site came back closed due to maintenance!

Just a coincidence I know, but what a time for that to happen.

M

Lol, They're on to you 

3 hours ago, Marvin Jenkins said:

Are there any other examples of galaxy pictures from Hubble looking like that. I am a Hubble image fan (aren’t we all) and I cannot ever remember seeing this before.

I will have a good look through the archive on the web and see if I can more. Do you  know of a link specific to that type of Hubble image?
 

Marv

Really? I thought this was very often how Hubble images are presented.

The Wikipedia link has other examples.

However, for many targets, depending on its angular size, you'll either see an image from a single quadrant, or the image will be a composite that fills in the missing bit.

3 hours ago, Marvin Jenkins said:

I did wonder about that possibility and MK 205 being in some form of optical alignment but there seems to be a problem. Taking into account all of the above and using the revised red shift to attain a distance of MK 205 surely means that MK 205 is impossibly large and bright.
Any thoughts?

Marv

You'd need to look at the figures, but you may need to consider the effects of gravitational lensing, as that can have a magnifying and brightening effect.

I'm not saying it is that in this case, but it's a possibility.