Need advice on filters etc. New to this.

[MikeOcall]

Ok, ill try and word this as short as I can, any answers bullet pointed would be appreciated as I hate reading pages of answers! I have just got a National Geographic 90/1250 Cassegrain. Managed to see a part of the Orion Nebula, and enjoyed finding it. Naturally I guessed better filters equals better views. So I've bought Celestron X-Cel LX 12mm and 7mm. 

• They seem to be dirty when looking at the moon, tried blowin the lens etc. Do new lens suffer from what look like floaties?
• i can't see the focus the 7mm sharp when looking at the moon? If I go over the max usefull magnification by a little will make that much difference? (Website says mine is 168x and with a 7mm it gives me 178x)
• They seem to take in far more light and I already have a bog standard moon filter. Are there different grades of moon filter, to take out more light? 
• Are these lens any good for viewing nebula?
• So far I've only viewed Jupiter etc through bedroom windows, sometimes for a few seconds I can see the red cloud belts etc. Majority of the time it's just a blurryish white ball. I know there will be heat and light pollution involved viewing this way. My question is, is it blurry etc the majority of the time because this is an entry level telescope, or because I'm viewing in the worst conditions possible, will it actually make much difference going out properly into a field somewhere?

Next section is about the scope itself.

• On side of telescope there is a 360' sheet, what's this for?
• when I'm trying to align telescope, I set date time and location. It then asks for Azi, Alt. How do I figure this out? It has range 0-360 range 0-90 too on that same screen. It's the go to system.

Any help is appreciated, I am literally new to this, had the telescope 2 weeks.

[dweller25]

Going outside and allowing your scope to cool will DRAMATICALLY improve the views

[MikeOcall]

I'll try this. Thanks David for the reply!

[brantuk]

Welcome to SGL Mike.

I'll second Daves recommendation to go outside with your new scope - give it 45mins to an hour to stabilise temperature and you'll see a huge difference in the views. The Celestron X-Cel's are nice eyepieces but I would stick around >=8mm so as not to exceed the max useful magnification of your scope.

Another tip - wait till Jupiter is high in the sky so you are looking through less atmosphere, which can give very wobbly views at times. Check the sky is clear and transparent but watch out for high level whispy thin cloud which you can't see, but works against you. And it's best to observe from as dark a site as possible with your eyes fully dark adapted (takes around 20mins). Good luck

 

[MikeOcall]

Thank you I'll try these steps.

 

are there different grades of moon filters? Or are they all the same

[Ricochet]

2 hours ago, MikeOcall said:

• On side of telescope there is a 360' sheet, what's this for?
• when I'm trying to align telescope, I set date time and location. It then asks for Azi, Alt. How do I figure this out? It has range 0-360 range 0-90 too on that same screen. It's the go to system.

1. If you mean the yellow ring with the numbers, it looks like it is there so you can read off the altitude (0-90).
2. You have to tell the telescope which direction it is pointing in. You can probably read off the az (0-360) from the compass if you put it in the eyepiece holder and the alt from the yellow ring but the easiest way to do it is to set the telescope up with the tube horizontal and pointing north (again use the compass) so that you can just put 000 and 00 into the handset. From the manual:

Quote

OTA (Optical Tube Assembly) Zero

Here you will be asked to provide the orientation of the telescope.

In the 'Azi:' field, enter '000'.

In the 'Alt:' field, enter '00'.

Open the Altitude and Azimuthal locking knobs. Adjust the telescope so that

the tube opening (2) is pointing directly north and is level. It is recommended

that you use the included compass (18) and bubble level to make sure the

device is positioned accurately. You can put the compass into the eyepiece

connection (3). Then retighten the locking knobs.

 

There are different strengths of moon filter. See the FLO Moon filters section for examples. A polarising filter might be best as you can adjust the darkness to match the Moon phase/brightness.

[laudropb]

It is seldom you can use the maximum magnification suggested for your scope let alone go above it. The atmospheric conditions will limit the magnification achievable. This also helps to explain the blurry views of Jupiter. If you are viewing through closed windows the window glass will also distort your view. You really do have to go outside.

[pipnina]

You may already know of this concept, but I'll explain it anyway as part of my response:

Exit pupil is the size of the circle of light you see coming out of the eyepiece from a distance (not looking down it). The size of it is the aperture of your scope (in your case 90mm) divided by the magnification (with the 7mm this should be 178x producing an exit pupil of 0.5mm)

0.5mm is a TINY exit pupil. The smallest I've ever used is 0.75mm and that was quite blurry. This small exit pupil could also explain your seeing of "Floaters". Those likely aren't in the eyepiece but in your eye.

As stated above, it's best not to observe through a window and to let the scope cool before using it.

[LukeSkywatcher]

All i can add to this is to say: "be careful how much magnification you use with the scope". Its a 90mm diameter/aperture scope?. I (as many others do) believe that a scopes maximum useful magnification is the same as the aperture (in this case 90mm)..........so a magnification of 90x would be perfect. You can afford to go a bit higher though. So i'd say your scope could go up to a magnification of about 140x (roughly). Any more and the views just become blurred. There are other factors which will cause blurred and/or sub standard views such as atmospheric conditions,viewing through a glass window (are there any other types of windows?.LOL),collimation and cooling of the scopes optics.

The Celestron x-cel EP's are quite good and a 7mm should be ok, but i feel it may be pushing what the scope can do slightly more than the scope wants to. An 8mm would work brilliantly (in my opinion). I use an 8mm with all of my scopes for observing planets and the Moon. I have a 6mm also and i have used it once simply because of atmospheric conditions. Doesnt sound like there would be a huge difference between (in my case a 6mm and an 8mm), but there really is. 

[John]

Personally I'd not use a moon filter with a 90mm scope. I don't use one even with my 300mm scope.

Getting outside, allowing the scope time to cool down and not using ultra high magnifications will make more difference to the views than anything else. After a while your experience at the eyepiece will start to make a difference as well

[Mak the Night]

I have a 90mm Mak at f/11.3 (1000mm f/l). Depending on the quality of your eyesight you should be able to utilise an exit pupil of around 0.5mm. I can achieve this with mine with an 11mm TeleVue Plossl and a 2x Barlow. This gives me a realistic absolute maximum magnification of 181x.

I have seen a figure of 213x often touted as being the absolute maximum magnification for a 90mm scope but unless you have very good optics (TeleVue?), atmospheric conditions, and the eyes of a bird of prey, it is unlikely you'd actually achieve that.

I believe your scope is around f/13.8, which is usual for most 90mm Mak's. To achieve a roughly 0.5mm exit pupil the shortest focal length that you could effectively use would be around the 7mm mark.

This would give you 178.5x as a maximum magnification. An 8mm eyepiece will give you 156x which is an adequate high magnification for a 90mm scope and anything around 150x will be the best for seeing planetary detail on a 3.5" scope. A 2x Barlow and a good quality 15mm eyepiece will give you 83x on its own and 166x with the Barlow. Your 12mm eyepiece will give you 104x. Which is a nice medium-high magnification for a 90mm and should, conditions permitting, allow you to see the rings of Saturn, Jupiter's cloud belts and some pretty stunning lunar views.

I tend to use an 18mm AH orthoscopic on my 90mm Mak often combined with a 2x Barlow to give me 55.5x and 111x. Jupiter is not an easy target anyway and can often be difficult to view. The Orion Nebula should look good at 55x. You are going to get some distortion and internal reflections if you view through an inside window, so that isn't ideal. For the best results the telescope needs to be outside.

I wouldn't use the Moon filter, many of the cheaper ones are far too aggressive even for a 102mm scope. A Baader Neodymium works well for me.

http://www.firstlightoptics.com/light-pollution-reduction/baader-neodymium-filter.html

[MikeOcall]

Wow I really appreciate all the advice and help guys! I was thinking of taking back he 7mm to be honest and replace with 9-8mm. Sadly the Celestron sights I have come in an 8mm!

 

Woukd an 9mm and good Barlow be better than just an 8-7mm EP. I thought the Barlow Woukd just distort the view.

I managed to see a part of the nebula near Orion's Belt a few nuts ago, but it was all blueish, like I could only see the top half of the nebula, is this filter or atmospheric conditions preventing me seeing the whole thing.

this scope sounds very beginner.. Will I get to see andromeda and a good selection of nebula giving the best conditions?

Thanks again for all the help!

[MikeOcall]

Do I even have the right aftermarket EP. I'm not sure about exit pupil etc and how it works! Trying to read up on it but not understanding!

[Ricochet]

The Celestron X-Cel LX has a 9mm in the range so seeing if the supplier would swap your 7mm for a 9mm might be a good idea. However, you really need to get your scope outside and cooled in order to properly test the combination of scope and eyepiece because the problem might be mostly you trying to observe from inside. You won't be able to use a 9mm eyepiece and a barlow because that will exceed the magnification limit for your scope.

Your view of the Orion nebula sounds about right for a visual observation. DSO's won't look like the detailed colour photographs that you might have seen and will usually appear as fuzzy grey blobs, although I see the Orion nebula as green. The best thing to do for viewing DSO's is to get out to a location with dark skies. Light pollution will wash out the sky from urban areas  and makes viewing such faint objects extremely difficult and to be honest your scope design is much better suited to lunar and planetary observation.

[Mak the Night]

2 hours ago, MikeOcall said:

Wow I really appreciate all the advice and help guys! I was thinking of taking back he 7mm to be honest and replace with 9-8mm. Sadly the Celestron sights I have come in an 8mm!

 

Woukd an 9mm and good Barlow be better than just an 8-7mm EP. I thought the Barlow Woukd just distort the view.

I managed to see a part of the nebula near Orion's Belt a few nuts ago, but it was all blueish, like I could only see the top half of the nebula, is this filter or atmospheric conditions preventing me seeing the whole thing.

this scope sounds very beginner.. Will I get to see andromeda and a good selection of nebula giving the best conditions?

Thanks again for all the help!

You couldn't use a 2x Barlow combined with any eyepiece with a smaller f/l than 14mm really as it would almost certainly exceed the resolution limit of your Mak. Barlow lenses are often derided for some reason, but it could be mythology based on cheap giveaway accesories, that are often included with 'starter' scopes. If you pay over £100 for a TeleVue Barlow it will do the job perfectly. On my tabletop 90mm Mak I find my TV Barlow is a tad heavy so I use a small, light Celestron Omni 'shorty' Barlow. It's quite decent, and gives decent images for a three and a half inch scope. A 90mm scope should quite easily see most objects either visible to the naked eye or a pair of binoculars.

This (Stellarium) is a pretty good approximation of what I can see of M42 with either of my Mak's. This is with a 102mm aperture with a 40mm Plossl at 32.5x. I can get roughly the same magnification with my 90mm Mak with a 32mm Plossl.

[mcsheffield]

The best advice you can be given, is to stop keep trying to change things.

Get outside, you can not view inside, and spend time getting used to what you have bought. Join a local group, get to view through other scopes, you will learn far more that way rather than keep changing at the beginning.

Many £££'s are wasted by rushing and changing this bit, that eye piece etc. You have to understand what you have and how to use it to the get the most out of it.

If you read on SGL some people mull over their 1st purchase for a long time, you need to get it right. you need to learn about viewing the night sky, when its good & when its going to be a wasted night. There are so many factors that effect what you will & can see, light pollution, other lights, the atmosphere, your equipment, getting it cool will also help. There is a wealth of knowledge & information on this forum, make the most of it. All our equipment has limits, you need to understand the limits of yours. 

Yes, you will get cold, but that's part of the enjoyment when you manage to find a new dso for the 1st time.

I am sorry If I did not answer any of your questions, but I am trying to be helpful & honest about wasting money when you don't really know what you have at your fingertips Understand that and you can move forward.

 

Andrew

[Jimtheslim]

I received a 90mm refractor f/10 as my first scope as a birthday present last year, here's a few things I've learned;

- As has already been said, get outside and let the scope cool down. I really enjoyed the longer summer evenings and starting to look at the planets during twilight. Look for where Jupiter should appear and see how long it takes before you go mad staring at blank blue sky, and then there it is! Seeing the moon and other planets against a blue sky always seems more 'trippy' to me for some reason and my frac really gives fantastically sharp views around twilight.

- Take your time and don't underestimate the usefulness of a red led torch and how much difference it makes to let your eyes adjust to the dark.

- I bought a few second hand Meade plossls and a new 99% dialetric diagonal. These definitely seemed to improve my views a little and were not massively expensive. The diagonal came in at about £50 new but I was easily able to see the difference when viewing Venus. In this game just a small improvement can seem like a massive jump!

- I also purchased a motor drive for the RA. This doesn't get a lot of use, unless I am looking for Jupiter's red spot transiting and know I will want to follow a single object for a number of hours. Again, at less that £30 it didn't break the bank and it tickled my curiosity for buying and fiddling with some equipment. 

- I borrowed a set of filters, including a moon filter and had a bit of fun with them but they rarely come outside now. More glass means less light hitting the eye and with a 90mm frac you need all you can get, I definitely wouldn't recommend using one for DSO's. As for the moon I haven't used the filter in ages and don't feel like I'm missing out.

- The same goes for the Barlow, I have 6.4, 12, 25 and 32 Meade plossls and these cover everything (although I would be lying if I said I wasn't constantly looking for a good 15mm). I can use 6.4 on planets when seeing conditions are very good, however this is rare although it comes in handy when looking for moon features. No doubt a good quality Barlow is a decent investment, but I wouldn't look to spend a great deal of money on one at this stage. Again, it's just putting more glass between your eye and the object.

- The Orion Nebula won't be as spectacular as the images you'll find when googling it. I see it as a feint off-blue smudge around several stars, when using the 6.4 you can easily split the 4 stars in the trapezium. These still hold a fair bit of sharpness when using the 6.4, but I like to see it with more surrounding stars at a lower power (if that makes sense).

- I've struggled to really confirm seeing many other DSO's from my garden. So grab a sleeping bag and wrap up the scope and take a drive to somewhere with little or no LP.

- buy a cheap, height adjustable stool.

[MikeOcall]

Just an update. Returned both the Celestron X-Cel EP, as they have cost £120. Gone to just basics and bought the Celestron omni lens. As I can get quite a few for the price of 1 of the others. 

I also have bought a Antares ND Moon filter, which seems 100X better than the standard that came with the scope. 

I left the scope outside for 20min yesterday, went out and viewed Jupiter with the 9mm omni. Was fantastic. Think I can really get into this when I know how to spot good conditions! 

Do light pollution filters make a great deal of difference? And any filters that may help bring out better colour in a nebula?

[Mak the Night]

As I live in the greenbelt, I'm not exactly sure of the efficacy of LP filters. I like to use the Baader Neodymium for contrast on lunar/planetary targets. I also use a Baader UHC-S filter for objects like M42 (Orion Nebula) but you will probably need an exit pupil of above 3mm to utilise it effectively. On a slow scope that could entail only a 30x (-ish) magnification.

[BritAngler]

Light Pollution filters do help somewhat with the sodium (orangey-red) streetlights, but not for the new-fangled white LED lights. A blue filter is said to bring out more detail when viewing Jupiter, but I haven't tried one yet to find out.

[Jimtheslim]

2 hours ago, BritAngler said:

Light Pollution filters do help somewhat with the sodium (orangey-red) streetlights, but not for the new-fangled white LED lights. A blue filter is said to bring out more detail when viewing Jupiter, but I haven't tried one yet to find out.

I have borrowed a number of filters and found that I spend so much time taking them on and off, wondering if I can improve the views with or without them that I neglect to simply take some time to actually look at what's in the eyepiece. I haven't noticed any significant difference in using filters on Jupiter, only a slightly dimmer image.

[Mak the Night]

I think the blue filter often used on Jupiter is a Wratten 80A. I've never had much luck with one. I just use a neodymium usually threaded into the diagonal nosepiece.

The Blue 80A are on the right.

I tried blue & green filters a few weeks ago on Jupiter with my 102mm Mak but I doubt I was getting a high enough exit pupil with the eyepiece combination I used and I abandoned the experiment.

[swamp thing]

20 hours ago, MikeOcall said:

 

Do light pollution filters make a great deal of difference? And any filters that may help bring out better colour in a nebula?

 

The best LP filter is a tank of gas. Go somewhere dark if you can buddy it makes a HUGE difference.  

[MikeOcall]

I'm getting to grips with most of this now I think. But I'm still really puzzled on what exit pupil is and how to work it out!

[John]

26 minutes ago, MikeOcall said:

I'm getting to grips with most of this now I think. But I'm still really puzzled on what exit pupil is and how to work it out!

The exit pupil is the bundle of light that comes out of the eyepiece. It's stated in terms of it's diameter in mm. To work out the exit pupil you divide the focal length of the eyepiece by the focal ratio of the scope. Example: a 30mm eyepiece used in an F/6 scope produces an exit pupil that is 5mm in diameter. Use a 10mm eyepiece in the same scope and you get a 1.66mm exit pupil and so on.