Raph-in-the-sky

53 minutes ago, Louis D said:

Yep, pretty much correct.  This all assumes that your eyepieces focus close to their shoulders (+-5mm is fine).  A counter example for me would be my 12mm Nagler T4 which focuses 19mm below its shoulder, so I added five 4mm thick 50mm ID O-rings and a 20mm 2" extension to the bottom of the eyepiece to make it closer to parfocal and still be able to be securely held in the focuser.  The difference in coma correction is noticeable.

For 1.25" eyepieces, just put an adapter in the CC and you're pretty much good to go.  Many 1.25" TeleVue eyepieces focus about 6mm below their shoulder, so the adapter would probably put the focal plane at just about the right distance.  The GSO CC is designed to have good correction from 70mm to 80mm of separation.  I don't notice much difference up to about +-10mm.  That 12mm Nagler is really the only eyepiece I have that really needs to be parfocalized.  Check your eyepieces to see how far they focus from their shoulder to get some idea about your own need for parfocalization.

Thanks for your answer!

How can I know where the focus point of an EP is? Btw you can see what EPs I have in my signature.

@Louis D @Alan White

From reading other treads I beleive that you guys have the GSO CC and maybe you could help me?

Hey guys,

I am (still) considering buying a GSO CC to use in my SW 250px. 

What I understood so far is that I would need 75mm from the top lens of the CC to the focal plane of the EP. This would be achieved by adding a 25mm spacer... Am I right so far? 

So am I supposed to put the CC straight in the focuser ? (without the 2'' adaptater)?

My second question is how do I use this with a 1.25'' EP? Am I supposed to add the 2'' to 1.25'' adaptater after the CC? Will that maintain the proper lightpass length?

Many thanks for your answers

Raph

OK, I'll pass on the 15mm screws.

Thank you all for your answers!

2 minutes ago, alacant said:

Hi

Yes. Confirmed: M4. You can also make adjustment (a lot!)  easier by fitting thumb nuts.

Cheers and HTH.

 

How long are those? The ones I might get (which are also tumb screws) are 15mm long (threaded shaft) + 2.38mm (head)... Seems allright, no?

Hello,

I just have a quick question. Are M4 screws the right size for a SW 250px secondary miror adjustment? How long should these be ?

Many thanks,

Raph

5 minutes ago, dragnscalearmor said:

Thank you all for the information. I'm extremely new to this (first telescope), so any advice is definitely appreciated. I will be watching the skies in July  and after for Jupiter and it's moons (evenings). I'm very excited to see them. I ordered a cell adapter from Amazon a few minutes ago so I can get some good pictures of the moon. I've been spending a lot of time looking at the moon, and it's just incredible. What a terrific hobby I have discovered! I have also purchased a telescope for my 8 year old granddaughter, because she's so fascinated with mine. I'm anxious to see how she does with it.

Thanks again, and I'll check out the 4mm and 5mm lenses. Really appreciate it!

Also you should download Stelarium. It shows you the sky you should be able to see from anywhere at any time. It's great to plan you evenings ahead.

And you should also consider getting "Turn left at Orion". It's a great book and is beginner friendly.

Hello,

First thing you have to know is that Jupiter is not visible right now as it is behind the sun for us poor earthlings. Next opposition (ie. the best time to view it) will be on 14 july 2020. So it should be visible in the morning 2-3 before this date and in the evening 2-3 months after this date.

Now regarding the items that would help viewing it, I would suggest a 4mm or a 5mm which should give you respectively a magnification of x150 and x120. As for what to buy, it will depend on the budget you want to allocate to this but one thing to keep in mind is that Plossl design at these focal lengh will have a very short eye relief and will not be comfortable to use. My advice would be to go a little more expensive and get either a BST starguider  (https://www.firstlightoptics.com/bst-starguider-eyepieces/bst-starguider-60-5mm-ed-eyepiece.html) or a skywatcher UWA Planetary (https://www.firstlightoptics.com/skywatcher-eyepieces/skywatcher-uwa-planetary-eyepieces.html). They offer about 60° AFOV and have comfortable eye relief.

Regarding filters, I would not get any colour filter but I would get a Baader Moon & skyglow neodymium filter (https://www.firstlightoptics.com/light-pollution-reduction/baader-neodymium-filter.html). That's far from mandatory and I would advise not to get it right away but only later if it still makes sense.

17 hours ago, Eugene69 said:

Hello, 

Yeah i dont really know what im talking about. I have only been using the telescope for about a month now. Im guessing that a quickfinder is an essential piece of kit? 

Thanks for the help!

I wouldn't say its essential but it's a great help!

29 minutes ago, Eugene69 said:

Yeah thats the one. Thanks for your information! I did look at the bst starguiders, just waiting on payday haha and i will definitely check out stellarium. The rigel quick finder looks nuts but i want to learn to navigate the sky the old school way first!

Thanks again

Hello,

I beleive that you are mistaken on what a Quickfinder does. All it does is project target on a piece of glass through which you can see the stars. You will still have to take out your maps and find what you want to see by yourself ... To me that's the old school way.

I would have suggested Telrad instead of Quickfinder but since it is likely that you upgrade you scope in the short/mid term (if you stick with astronomy) Quickfinder is better since it comes with 2 bases.

Just received a 32mm Panaview... My first 2'' EP! 

Thanks again to @RiponJas

And BST starguiders are great value for the price!

For widefield low power, you could have a look at a 32mm Panaview. It's supposed to be pretty good in 70%-80% of the field at f5 (with 70° AFOV) and you can pick one up second hand for £50.

I can't give you first hand experience as I'm supposed to have mine delivered today.

+1 for buying "Turn Left at Orion"

BSTs are great! Those were also the ones I bought as a first upgrade and I'm still very happy with my 5mm and 15mm. 

I also don't like narrow views and I think that 60° to 82° is the sweet spot for me... never tried a 100° EP but I think the price would be to steep for me.

How about a 10mm Televue Delos? That's just in your budget and FLO have a 10% discount right now.

16 minutes ago, Rob Sellent said:

This is just a guess, Raph. No doubt I'm going to be wrong but bear with me. 

• unbranded 7-21mm
• probably has four elements
• 7-21mm zooms tend to be (not always) inferior in reviews
• my guess its apparent field of view will range from around 43º degrees at high power to 30º degrees at low power
• edge perfomance won't be perfect
• might introduce chromatic aberration
• won't be as sharp or as contrasty as a fixed focal length eyepiece
• probably retails new at less than €50
• mechanically it should be okay, useful in your BVs, at star parties or when bound by laziness

The idea was buying 2 of them second hand (only £20/p) to use with a cheap BV... I think it will fit the bill.

This will come much cheaper then 2 or 3 pairs of plossl which I might get later on if I like the BV experience. Worse case I'll resell everything at the same price.

Let's try this again... Can you guys see it now?

Hello,

I was wondering if anyone knew this zoom and if it was any good? It's a 7,14,21mm 

Cheers,

13 hours ago, CentaurZ said:

 

An inferior planet (Mercury or Venus) alternates as an evening or morning star, i.e. visible shortly after sunset or before dawn.

The entire synodic cycle for Venus is 19.2 months, half in the evening and half in the morning. For Mercury a synodic cycle averages 3.8 months. A synodic cycle is the time it takes for one planet to lap another in their race around the Sun.

Venus will indeed be visible in the western sky during the early evening from now through May, as illustrated in my chart above. Its angular diameter is widest during inferior conjunction with the Sun, but at that time it cannot be observed.

Below is another chart I created that may clarify the matter for you.

 

Thanks! That was a great explanation! I knew the jist of it but I was missing a time frame.

One more question... When does Venus become decently observable in its cycle coming from supperior conjonction? If I understand correcly the planet is observable in the evening about 6 month before inferior conjonction, becomes unobservable for a short time (how long?) close to inferior conjonction and then becomes observable again for about 6 month in the early morning... Am I getting this right?

On 29/11/2019 at 22:39, CentaurZ said:

Brilliant Venus has commenced its apparition in the western sky after sunset following its superior conjunction behind the Sun on 2019 AUG 12. It will become its highest and brightest during the upcoming spring.

Photos and descriptions of Venus during this apparition would be welcome additions to this thread.

 

Hello,

I struggle a bit to understand when I am supposed to look for inferior planets. Could you please help me with this?

Is Venus going to be observable during the whole spring, every day? Evening or morning viewing? When will the disc be the widest (viewed from earth obviously)? 

Cheers,

Raph

9 minutes ago, Greyhoundfan said:

I did wonder about one of these as my first bit of astro gear!

https://www.amazon.co.uk/Electric-Clothes-Heating-Motorcycle-Rechargeable/dp/B07MLZTN95/ref=sr_1_8?dchild=1&keywords=heated+coat&qid=1575460576&sr=8-8

Dave

That seems interesting. I have no experience in using these but if you decide to buy it can you please let us know if it's worth it.

You should also learn about the main asterism (not constellation but easily recognisable shapes): Hercules, Pegasus, summer triangle,...

Have a look at this! https://www.constellation-guide.com/category/asterism/