"Cool down," reflectors, and other newbie ponderings

[KateIsSirius]

Hello all,

I'm working toward purchasing my first telescope, which I believe will be an Orion Starblast 4.5 newtonian reflector on a tabletop dob mount. I wanted something portable and small enough not to take up too much space in a tiny urban apartment. However, I have some questions (some really dumb questions... bear with me.)

The more I research Newtonian reflectors, the more I read about "cool down" or "cool off" time. I'm guessing, then, that reflectors heat up with use? I know this might be a completely idiotic question, but I just wasn't sure of this. I know about having to collimate the mirrors in a reflector, but the cool down time I don't know so much about. Is the cool down time more relevant to some of the bigger Dobs (and I've seen some of you dude's Dobs, and I must say... I'm impressed. Haha) or does the aperture/mirror size not matter?

Also, if anyone else has experience with this particular scope (Orion Starblast 4.5), I'd be super happy to hear your thoughts or advice! Actually, I'd love thoughts and advice on anything. I'm so so excited to begin this hobby, as I've loved studying the planets and stars for so long... but as a 25 year old female, I don't have too many friends who share my fondness for space. I've been annoying them for the past few weeks rambling about telescopes.

[ghostdance]

It's a great little tabletop scope! Was my faithful companion for my first year stargazing. I then bought the Starblast 6i - the 4.5's older brother (or indeed sister There's my quick rundown on the 6i that mentions the 4.5 in Members Reviews section).

With the 4.5 you'll get really nice views of starfields and clusters, the larger planets will be small but quite detailed depending on sky conditions and eyepiece. If you have dark-ish skies, the 4.5 is capable of showing you some of the fainter DSOs...not as much as an 8" or larger, but then they're not as portable...

Cool down is nothing to worry about with the 4.5 - having a small mirror and tube, the scope cools down in 15-30 minutes max.

The 'downside', so to speak, of both the Starblasts is the focuser. It's basic. But that's not to say it's unusable - it does the job and can be easily fettered to be a whole lot smoother.

The upside is great views, good optics, easy portability and storage. Great little scope to learn the skies with

Steve

ps Where are my manners?! Welcome on board the good starship SGL. Have a great voyage!

[cuivenion]

To expand on cool down the telescope has to reach ambient air temperature before you can get the best views, as you're taking the telescope outside from a heated house the scope has to 'cool down', which as ghost dance says won't take long with a scope that size.

[MattJenko]

Welcome! Some good advice from previous posters as always. Air currents cause disturbances and wobbly the views. Its like looking through a heat haze. Cooldown time is merely the time taken for most of the air in the tube to stop moving around so much. It doesn't mean you can't use the scope straight away, it just means that your views will be less turbulent (and therefore better) after a few minutes of the hot air escaping and the warm mirror cooling enough to prevent it causing those air disturbances. Bigger mirrors mean longer cooldown times, and closed systems like Maks + SCTs take even longer.

Enjoy your new hobby. I am a recent convert, and just wish I had started sooner!

[Earl]

The trick with cool down is to try and store the scope as close to ambient as possible.

I read your in an apartment so not sure if that is possible? do you have a cooler room than others?

Newts are not as badly effected as a sealed unit scope like an SCT or MAK and you can install a PC fan on the bottom of the scope to help shift out any warm air prior to use, bu do turn it off after as it will cause unstable air in the tube.

however saying all that, to start with id not get too worried about it until you want to refine your telescope use.

[jetstream]

Welcome to SGL!

Cool down and collimation are extremely important for planetary and lunar observing. The length of time for cool down depends not only on the scope aperture and design, but also "how cold it is outside". My scope's will take far less time to cool now than in -30c in the winter, I mention this to you as I see your in New York, which can get really cold at times.

Give your scope a good half hour to an hour in the winter. When cooled and collimated your scope will give very nice views.

Speaking of collimation, what method are you using? This may start a big debate, but what the heck- another round will be interesting!  Hint: Myself and numerous others love and use Cheshires....

[Piero]

Then the other issue is when they cool down too much! 

[jetstream]

Then the other issue is when they cool down too much! 

Piero, I'm curious what you mean?

[Piero]

I meant that telescopes can also become colder than the air outside and if not controlled they can get soaked with dew. 

The OP is about the problem of cooling time. I simply wanted to mention that telescopes can also suffer from excessive dew formation when they cool too much (or too fast).

I should have said this explicitly. Apology for having been unclear.

[jetstream]

Thanks for the explanation Piero, I was just wondering. Cooling can be an involved subject - the main thing is it gets cooled to or near ambient. Dew can be controlled but an uncooled scope will not give good high resolution images or split stars well.

I actually asked this so the OP doesn't think there are negatives to cooling- it is a must. If she is in a city the planets/moon and star splitting may be a main set of objects to observe.

[KateIsSirius]

Ohhh, I see, so the "cool down" simply refers to getting the temp inside the scope to the same temperature it is outside. Makes a lot of sense! I probably won't have to worry about that too much right now, since NYC has some toasty summers.

And as for collimation, seeing as I don't even have my scope yet, I haven't tried collimating. I'm sure I'll have lots of questions when I try my hand at it-- reading about something is different from the hands on experience, of course.

[KateIsSirius]

And thank you to all who responded to my questions-- everyone seems so friendly and helpful here!

[jetstream]

Ohhh, I see, so the "cool down" simply refers to getting the temp inside the scope to the same temperature it is outside. Makes a lot of sense! I probably won't have to worry about that too much right now, since NYC has some toasty summers.

And as for collimation, seeing as I don't even have my scope yet, I haven't tried collimating. I'm sure I'll have lots of questions when I try my hand at it-- reading about something is different from the hands on experience, of course.

I would seriously consider using a Cheshire tool for collimating your future scope, regardless if many recommend lasers and collimation caps. It is easy, cheap and works. Just my 2 cents...

Also you may want to explore the subject of sky conditions ie seeing vs transparency in a new thread and the effect of rooftops etc.

Have fun!

[knobby]

Hi, don't worry too much about cool down time, you can use the scope pretty much straight away... it just gets better as it matches the outside temperature.

Start by looking at something big like the Moon and as the scope 'cools' the view should start to get steadier, then go for more magnification...

most of all, enjoy it !

[Tinker1947]

Hi, don't worry too much about cool down time, you can use the scope pretty much straight away... it just gets better as it matches the outside temperature.

Start by looking at something big like the Moon and as the scope 'cools' the view should start to get steadier, then go for more magnification...

most of all, enjoy it !

This.........

[Polstar_UK]

I've had the Starblaster 4.5 for about 2 weeks now. I'm finding it great to use and getting some good views. The moon looks great, I saw some nice details of craters. The planets as previously mentioned do look small but you can make out detail on them. With the 6mm EP you can see venus phases, Jupiter as a disc and the moons and Saturns rings. I got a x2 Barlow with the scope and can see the cloud belts on Jupiter as faint lines and the small gap between Saturn and its rings. The 15mm EP gives good wide field views of stars, I've not seen any deep space objects yet but that's down to my lack of finding skills.

I've also bought some extra EP to go with the ones you get with it, the Expanse a pretty good line of EP so I got the 9mm from Orion. This compliments the other two nicely.

Jupiter and Saturn looked really good with a 5mm and 2.5mm EP, they lacked colour but you could make out the basic detail better. That said this telescope is better at deep sky than planet viewing from the reviews I've read.

[ghostdance]

It's a fine little scope, glad you're enjoying it Polstar Almost makes me feel like keeping mine but my wife would (rightly) not, er, exactly *appreciate* me accumulating a bevy of telescopes